Two PCs with the same restore partitions are these interchangable

Hi, I am not too technical but will try to give as much info as I can.
I have two Medion PCs bought at the same time so basically mirrors of each other. I had a problem with the HDD being noisy so replaced the 1TB HDDs with Intel 180GB SSDs, all quiet now.....
So far so good, I used Intel migration software so the recovery partitions were also copied.

I now want to re-use the old HDDs as secondary drives, one was quiet and the other noisy, but would like to use all of the HDD but would lose a possible second backup of the recovery partition.
So what I would like to know is if these partitions will work in any machine. So if I just keep one (on the old noisy drive kepy in a drawer) can I use that on either PC if it fails ?

I still have the recovery partitions on my SSDs but wouldn't mind removing that to free up space, so even more important to have a copy of the original recovery partition.

Basically I don't know if these are different on all PCs or the same one on all of them. So in my case if a PC operating system did fail in the future I could just pop in the dodgy HDD and restore from there regardless of which PC it came from.

I did back up the OS as required but this all went on one DVD so I could restore from this anyway ?
Not sure about that.....
I can't understand why the recovery partition uses 18GB of storage yet a Win7 install DVD is only one disc ? Same as the recovey DVD I created for each PC, only one.
So if everything goes 'Pete Tong' can I really just put in the recovery DVD I created when setting up the PC, press start and all will be well ?

Never had to do a restore in anger (did a couple when setting up but not as a result of a system failure) and hope I never will. Just trying to be sure I can recover should I need to.
Any information appreciated.

Thanks for replying, I knew I would miss something out.
I had the PCs running having bought them new (Medion Akoya 2039 models) so switched on and the OS installed. I then copied my stuff, photos etc, from an external drive I had them on.
When I bought the SSD I use the Intel toolbox and copied all of this from the old HDD to the SSD. Clever stuff, just hit go and it copies, swap HDD for SSD and it woke up like nothing had happened.

Problem was with the 2nd PC where first HDD had the 'click of death' so I returned it. Replacement had a 'humming' HDD which implies an out of balance disck or dodgy bearing.
Like you said, I didn't trust it to last long. Not as bad as the clicking one but eventually the bearing would fail. That is why I thought I would use it as a 'keep in a drawer and forget' type backup. Ok to use it occasionally but not to leave it running.

The first HDD was fine, totally silent, so I have reused that for video editing. I would like to use all of it though hence my question about deleting the recovery bit on it.

I am just triple covering any future problems as if the current OS has a problem I cab restore from the recovery partition on the SSD. If the SSD fails I can (I assume) just fit a new one and use the recovery DVD I created which will restore the original version of Win 7. If this doesn't work I can just put in the old hard drive and start again from there.

Not bothered about data as I back that up regularly, just reinstalling the OS as it came from the manufacturer. Just because I am paranoid doesn't mean all of the above couldn't happen

I have a set of leads that allow me to use any HDD as external but when I look at the HDD I removed using this it says it needs reformatting. Maybe because it was a system disc ?
I would like to do this and use all of the disc.

My main problem is that I am unsure how these recovery partitions work, I tried copying all files in one of them but the copy was slightly smaller than the original so not sure what happened there. I am guessing I can't copy the files only, that there is something else in that partition that I can't see. Tried show hidden files but nothing else showed up.
Folders in this partition are Recover, Tools and Drivers, plus files pass.rpt and swftcon.dat. Is that all I would need ? nothing missing.

I would only be using the original recovery partition to restore to the PC it came with.
I would try it and see what happens but all working well at the moment and I don't want to mess things up. Just don't want to re-use the recovery partitions then find I can't use the recovery DVD I created without them.

I would guess the DVD I created would restore the system to an empty HDD so should work anyway. These are meant to restore the system if the HDD dies ?
I did try microsoft to read up on this but very confusing, I couldn't find a single place where someone simply said - put in recovery disk, press on switch and it will load no problem. I would hope that would be the case ?

Thanks, I think the idea of downloading an ISO version of Win7 is the simplest thing to do. As you say I have the keys on the PCs so no problem there.

I bought Intel as they seem a well respected brand and also the procesor is Intel so I thought it couldn't hurt to keep them the same. Sure it doesn't make any real difference but if these processors and SSDs can't communicate properly what can ?

HDD is an Hitach HDS721010DLE630, not the best as 2 out of 3 have had problems. First was and is perfect, second had click of death and humming, last one just had humming. so 66% failure rate.......
The Medion PCs were good but had many problems, HDDs, DVD-CD readers (Samsung) old model and couldn't read all CDs I tried.
Basically as Medion were trying but failing to fix things and Samsung couldn't care less I figured I was better off to void the guarantee (such as it was - 'return for repair') and fix it myself. Hence the SSD conversion as it was easier to just replace them, PCs were only 2 weeks old but not expensive so I thought what the hell and fixed them myself.
Now just a bit paranoid something else will fail, but ok for over 2 months now so any electronics that last that long usually are ok. As you said I don't think I have anything to worry about.

It is just that I like to know the anser before I get asked the question, so if the PC had a problem I could always restore to factory settings and hopefully fix it. Just making sure I had everything yo hand just in case. Downloading the ISO Win7 is it I think, Thank you.

I did look at a Seagate external HDD, main selling points were only 500GB and didn't need an external power supply. I may buy one yet. Seems the 500GB size of anything is getting harder to find.
I di have an old style 250GB Seagate external drive bought years ago, very good but takes some setting up as it needs a power supply.

I thought since I had two brand new HDDs I may as well use them, the good one (now internal in my PC) for video editing as may as well use the space. The dodgy one (external via 'patch' leads) for general backups of photos etc.

Massive hard drives do seem a bit much unless you really need them. The SSDs I bought are 180GB (20GB used for recovery partition) and currently only 70GB in use for the OS and various photos and music. For general net surfing and computing there are fine, the speed difference is well worth it, I could never go back.