windows7 paint for vista

I'm not sure of what this paint ribbon you are saying is really. Can you tell what is this paint ribbon again?

To utilize that 16GB of RAM you will need a 64bit OS.

I believe your windows vista hard drive would work if you simply transferred it over.

I would highly recommend windows 7, it is alot faster and more reliable than vista and of course it will NEED to be 64bit otherwise you will only be able to utilize 3.5GB of RAM from that system, so the rest is such a waste :
Both of your other hard drives SHOULD work as long as you have to correct connectors on your new motherboard, however you may need to insert a windows installation disc and run "startup repair" to re-write the boot sector again, or i would recommend "Formatting" the drive you wish to boot from and installing a fresh copy of the Operating system onto it.

I too am a great fan of the MS Paint on Windows 7. Its so much better than the ones on XP and Vista to me.

In theory, you have to copy the mspaint.exe file from the C:\Windows\System32 directory on a Windows 7 machine and copy that on perhaps another directory on your Vista machine cause the old Vista Paint exists on Vista's C:\Windows\System32 folder. Right click it and make a desktop shortcut. Then try to launch it.

But I doubt this will not work because I experimented this last year. I copied the mspaint.exe file from Windows 7 to a Windows XP machine and it failed to work from there. However, Windows XP's Paint works with Windows 7 cause Windows 7 has backward compatibility. In the case of Vista, I don't know.