So in my continued adventures with this issue, I reformatted my harddrive and re-installed Windows XP (64 bit version this time). I also installed the latest version of Reaper (the 7/9 release)
The only drive available for my soundcard (m-audio 2496) on this OS is beta.
Sadly, now that I've gotten it up and running, Reaper (and no other audio program so far) crashes horrifically. Whenever I move to another window from Reaper (including ones that Reaper opens such as the render window), something goes wrong.
After I've switched back to reaper, the next time I try to do anything within a menu (such as changing options/configurations, etc.), Reaper completely freezes up. I have to hard reboot the computer to kill the process.
The only workaround I've found so far is that recording undoes whatever went wrong temporarily. I went to Reaper chat to ask about it. They said it was probably a driver issue (which is probably correct), but since it only affects Reaper, I think there might be something wrong on your end too.
I'm thinking of rolling back to an older version of Reaper. Might that help?