Moving a HDD with installed hardware drivers from the old system system into a new system/motherboard might work - if you can Repair the installation with the correct hardware drivers needed for the new system. There might be enough generic drivers included on the OEM installation disk to finish the repair.
You'll probably get a FAIL TO START message.
There will be no problem using the migrated HDD as extra storage. The data and user files will be available, just don't expect programs on that HDD to run. You'll need to install the software again.
There is still the license issue because an OEM version of a Win OS is 'married' to one system and the license is non-transferable.
Replacing the motherboard requires a new licence, as WR2 said OEM is locked in to the original mb, unless it's being replaced with the same or similar model because of failure.
So while the system will (should) boot ok, you will need to upgrade the drivers for the new board. Programs and data won't be effected.
That leaves you with the problem of the licence, you will have 3 days in which to fix it, ie; buy a new licence.
The retail version will allow you to transfer it to another pc or upgrade to your hearts desire, although there will be times when you may need to call Microsoft to reactivate.
Okay i think i will just keep that drive in my old computer and call xfx for a replaecment MOBO and ill just get retail windows 7 home .....(i dont think i need pro) also i wanted to know dies the retail come with both 64-bit and 32-bit
The retail (full and upgrade) package will have both the 32bit and 64bit versions.
It's not likely you'd need the Pro edition of Windows 7.
You're might have to reactive your Windows 7 installation even if the replacement MB is the same model. If the OS asks for a reactivation and the online method fails you could end up using the Phone activation method.