Installing software on new SSD

Naive question - I am considering buying an SSD to speed up booting and programme opening times. From what I have read, the essential files to put on the SSD to achieve this are - The OS and programme files (currently on my HDD under 'Programme Files' and 'Programme Files (X86') Folders). The general suggestions seem to be to do a clean install of the OS and use third party software to migrate the other files from the HDD to the SSD.
The latter being complicated by the fact that most software will not migrate individual folders. The size of files on my current 'C' drive is appreciably bigger than any SSD that I could afford.
My question is - If I install the SSD and disconnect all other drives, then install windows onto the SSD, the SSD will become my 'C' drive. If I then reconnect existing HDD (which Windows will label with a letter other than 'C'), why can I not simply drag and drop the two Programme File folders (together with a few other files and poss games) from the HDD to the SSD ? I could then, for the time being, leave my HDD intact with a copy of Windows on it so, should the SSD fail at an early stage I can simply remove it and continue using my HDD?
It would seem a reasonable way of doing things as Windows is not worried if the C drive is an HDD or a SSD.
Thanks in advance for any clarification.

why can I not simply drag and drop the two Programme File folders (together with a few other files and poss games) from the HDD to the SSD ?

Basically, all Windows-based programs have to be installed so as to put their files in the proper place, create the Start Menu items, copy support files such as .dll's to the proper place and the most important, create the Registry entries that Windows needs for how to run those programs.

Many thanks for the replies Berton and WHS. I can now see the logic and understand why drag and drop will not work.
From what you say, if I reinstall Windows onto the SSD I would susequently have to reinstall each and every programme that I have even though some that are used infrequently would be reinstalled to the HDD. In particular, would I have to reinstall email (WLM) or would my existing emails stay intact on my HDD?
Sorry for all of the questions but I am already thinking that installing an SSD may not be worth the effort or the risk of losing data.

Dandoodle said:

From what you say, if I reinstall Windows onto the SSD I would subsequently have to reinstall each and every programme that I have

Yes. That's what "reinstalling from scratch" involves... installing Windows/drivers/updates, and also installing all 3rd-party software.

even though some that are used infrequently would be reinstalled to the HDD.

Don't understand what you're saying here.

Normally \Program Files goes to C by default, and to keep your life simple and understandable and consistent there's really no reason to selectively change this, no matter what the software product you're installing.

In particular, would I have to reinstall email (WLM) or would my existing emails stay intact on my HDD?

You're mixing up two things here... (a) the programs, and (b) any data associated with the ongoing use of programs.

Just as programs normally install by default into C:\Program Files (x86) for 32-bit programs (or C:\Program Files for 64-bit programs), most programs commonly save any data you might save into some application folder within C:\Users\<userid> (which is the Win7 analog of the old C:\Documents and Settings folder on WinXP). But most programs will also allow you (at "save as..." time) to redirect the "data folder" location for saving data to some other folder or even on some other partition than C. It doesn't have to go into C:\Users if you don't want it to. But commonly, by default, that's where the initial "save as..." target normally goes for user data.

Anyway, the WLM programs would need to be reinstalled in your from-scratch install to SSD. And by default if you do nothing else, your new WLM installation will start with nothing in your new local WLM mail user data folders which will be created by default on the new SSD in its C:\Users folder.

But if you want to preserve your existing WLM mail folder data, before erasing your existing spinner you can just pre-copy (before installing WLM on the SSD) or post-copy (after installing WLM on the SSD) the existing WLM data folder from your old spinner (found somewhere down in C:\Users on the spinner) into the exact same folder location on the new SSD C's C:\Users. Then the next time you open WLM, it's almost guaranteed certain that the now existing WLM data folders you had previously built on your spinner will now be recognized by the newly installed WLM on the SSD.

Although this isn't 100% guaranteed, for most software products this approach can be used... to simply copy your existing data from your old spinner Windows system (most commonly found down in C:\Users somewhere) onto the matching folder location on your new SSD Windows system.

In a more generalized environment, where you use your C-partition just for Windows and programs, and use \Users minimally for data but instead have "data" placed elsewhere on other partitions/drives, the concept is the same of wanting to continue to use your currently existing data and not lose any of it, when you reinstall Windows. If the data location is on some other partition like D, or E, etc. (placed on a second drive, such as perhaps a re-purposed hard drive when you add an SSD for Windows as you're doing here), then you have to do zero to make use of it except to "point to it" in the "open" or "save as..." dialogs. It's only because you currently have your WLM data on your old spinner C:\Users that you have to explicitly do something to preserve it for your new SSD install.

Many thanks Dsperber for such a comprehensive reply. I appreciate your patience in explaining the difference between programmes and the data that is produced by using them and, aqs long as the programme is told where the data is stored (even if the programme is on the SSD and the data on the HDD) then there should be no problem.
The part of my question where I managed to confuse you was that with limited space on my SSD, I was thinking down the lines of leaving some programmes on my HDD instead of reinstalling them on my SSD. Having looked at the size of my programme files, I see that this option would be unnecessary as the two Programme folders only add up to 4 Gb.
I really do appreciate the advice that I am getting.

Dandoodle said:

I was thinking down the lines of leaving some programmes on my HDD instead of reinstalling them on my SSD.

But as has been pointed out, you cannot typically just "run" old previously installed programs from an old \Program Files location on your old HDD from your old Windows environment, while running under the newly operating Windows on your SSD.

You must truly reinstall the programs into your new SSD Windows environment, in order to newly create all of the Registry entries, program/data folders, install any DLL's into Windows folders, etc. This only happens at program installation time and all of it together is what truly makes the program "runnable" under the operating Windows, so don't think that it's just a matter of running the old program's EXE from old \Program Files on the HDD.

Now as you've already determined, there's really no reason to be "overly frugal" about whether or not to reinstall some of your less commonly used programs onto your new SSD because of space considerations. Much more important is whether or not you'll really ever use these old programs again. As long as you still have the installer file you can always install it (if you need it) in the future, so for now just bypass reinstalling it if you have a very low likelihood of really ever using this program.