1) What speed is your WD Blue drive -> RPM's really make a difference for your OS drive.
2) Partition and format your 2TB HDD ... the sector boundaries are gonna be all messed up, so you'll have to do it again later using Windows 7, you just need a temporary place to stick your doco's & stuff.
3) Stick the Windows 7 CD in, and run the migration wizard/Windows Easy Transfer from the windows 7 Disc ... it collates all your files, locally stored emails, address books & etc/etc and store it on the new 2TB HDD. Take note of what programs you have installed (it gives you a report at the end).
4) Do either of :
4a) Reboot, get into the bios & change the HDD boot order.
4b) Turn your PC off. Open your case and switch the cable connections between your boot 74GB Raptor HDD & your 500GB HDD, because if you reflash your bios at some point, you don't have to remember to reset the boot drive order
5) Install Windows 7 to your 500GB HDD, partitioning it however you want.
6) Install all programs that you noted earlier ....
7) Run the Easy Transfer wizard, and point it to the files that you stored earlier.
8) Repartition your 2TB HDD using windows 7 -> Delete all existing partitions.
9) Wait 2 weeks before reformatting your 74GB WinXP install, in case you've missed any files.
You can also do the bios thing first, install Win7 to the 500GB HDD, partition the 2TB HDD however you want, go back to bios, change back to the 74GB HDD, boot, run the Easy transfer wizard in XP, reboot, change the boot HDD, boot back to Win7 .. restore doco's from the easy transfer backup .... but that would mean getting into bios multiple times .. which i guess is easy enough .. just seems like more screwing around.
It is NOT necessary to unplug other drives during OS install ... ON THE PROVISO that you HAVE changed the boot order in bios to make your OS drive the first boot drive.
If you didn't change the boot order in bios (and accidentally left it as the 74GB Raptor), windows 7 will install it's boot loader to the 74GB raptor .. and all the windows/system files & folders to your 500GB HDD. If you then remove the 74GB HDD, or change the HDD boot order in bios ... your PC will sit there and look at you funny, because it can't find the boot loaders.
You can re-assign drive letters for all drives/partitions except:
1) The boot partition -> This partition is nominated "C:"
2) The partition that windows system files reside on (for the currently running OS) -> usually nominated as "C:", but may be "D:" if the boot partition is not the same as the system partition.
In most computers, 1 & 2 are the same -I understand that Windows 7 forgoes the boot partition with it's boot loader.
Something I find handy is that you can mount entire partitions in an empty folder .... I love that