Manic_Skafe, is the following what you did? I'm guessing no...
"You'll be fine.. Just boot off the Win 7 disc and start the install process as you normally would than once your at the partition manager just select the HDD you wish to install 7 to then let it install.. Once it's done you'll encounter the Boot Manager each time you boot up your machine.. This is where you choose which OS you want to boot into..."
If not, then you can either reinstall Win 7 following the instructions above (Both hard drives plugged in and working), or get a boot loader. Here's a link to one:
Download GAG 4.10 - free boot manager. Allows boot of up to 9 different operating systems - Softpedia
I have not used that boot loader so it's not a recommendation from me, just an option. I hope this helps you, maybe others will chime in with some better ideas. I only use the built-in Windows boot manager. To be honest, if I was you I would just start over. Best of luck! Windows 7 is definitely worth the hassle. After a couple of weeks I bet you won't even want to look at XP.
---------- Post added at 06:15 PM ---------- Previous post was at 06:12 PM ----------
I'm using Build 7229, x64. But the RC is probably fine for you. That is unless you are comfortable with Bit Torrent and checking hash numbers.