Partitions missing in WinXP - help!

Okay, so I've gotten myself into quite the pickle.
My problem is that WinXP SP2 can no longer see 2 out of 3 partitions on my main hard drive. It can see the Windows (C:) partition just fine, but the D: and E: partitions have both disappeared and now say "unallocated space" in Disk Management. So this is how I got to this situation...

My system was running WinXP SP2 just fine with two IDE Maxtor drives, both connected to the primary IDE channel. I was doing some stuff in the registry in order to remove all Microsoft Intellipoint mouse driver entries, following this guide: http://support.microsoft.com/kb/321122/EN-US/

When I restarted my computer, suddenly I was greeted with the dreaded error "Hard Disk Boot Failure Insert System Disk Press Enter". I tried a number of steps, like going into bios and checking the boot order, unplugging the slave drive. Finally I booted up my WinXP CD and went into recovery manager.

I tried CHKDSK /P and FIXBOOT on C:\, and both tools reported they fixed some errors but neither of them fixed the boot failure problem. Finally I ran FIXMBR on C:\ and voila, I could boot back into WinXP!

But now I'm stuck in my present situation. After fixing the master boot record, it seems that I've "lost" my D: and E: partitions. My WinXP C: partition is fine, as is my slave drive F: which is all data. I'm really hoping there is an easy way to fix my problem -- please don't tell my all my programs and data are lost!

Any help would be greatly appreciated. Thank you very much.