Windows 7: I am running two OS Windows7 & Vista and..

I installed Windows 7 on D drive. Every frequently-used programs are still in my C drive. Installing all those programs again takes not only time but also storage. Is there any way to benefit from C drive??

I apologize but I am misunderstanding you...

Windows 7 on D:\
All the installed programs on C:\?
Where is Vista at?

Haven't tried this in Win 7 so not sure it will work. Here is how I did it when I dual booted with Vista and XP. As long as all the applications you are using are the same version this should work (not saying it will), install the application (e.g. MS Office 2007), into the same folder on the c: drive that MS Office is already installed. Now, first attempt to do this with a application that is not truly essential. Let us now how this works. Again try it with something that isn't all that important just in case it doesn't work.

Many programs can be used from another install. Many can not and need registry correct for them. i.e. installing them.

Rule of thumb: The simpler they are, the more likely to be able to be used.

Vista is at C drive. I just wanted to run MSN, torrent etc which are already installed in Vista.

By the time that you copied the file, registry settings, user settings etc. etc. you could have reinstalled them from scratch and been up and running... Life is hard enough, dont complicate it un-necessarily...

+ 1

Although, copying user settings after a fresh install is sometimes quicker than starting from scratch.