You mention installing Windows XP (the 32-bit edition) after having Windows XP Pro x64. Did you attempt an "in-place reinstallation", using the 32bit version --- or did you create a separate partition, and install the 32bit Windows to that?
I haven't seen any reference anywhere that mentions it's possible to do an in-place reinstall of 32bit over the 64bit version. I believe it's always recommended to install to a completely separate partiton.
Which leads to my next question: Is this what happened? -->
1) You installed Windows XP 32bit onto a new partiton
2) Your music and movies were OK because they resided on their own, separate, partition
3) You then moved the remaining Windows XP Pro x64 files into a Windows XP 32bit created partition - naming it "old" -- and subsequently have lost access to those files.
If so, try pointing PC File Inspector ( http://www.pcinspector.de/file_recovery/uk/welcome.htm
) at the directory containing the x64 data you had hoped to keep.
I'd try PC File Inspector first. If it fails, another idea would be to try to gain ownership of the directory - though I'm not sure that this has much of a chance, since the differences between x64 and x32 are so great. It's worth a shot, I suppose --- http://support.microsoft.com/default.aspx?scid=kb;en-us;308421
[I prefer to gain ownership logged on as "Administrator" in Safe Mode]
If you find yet another alternative that works, post your results, as there may be another user with the same situation that can benefit from your procedure.
. . . Gary