Ok, I found something for you. It's probably going to take some regex work to pull out what you want, but here's what you need:
There's a partition utility in XP called diskpart. You will need to make a seperate script to run against this utility. I created C:\disks.txt. Inside that file, there's one line:
list volume
Then from the command line, run diskpart /s C:\disks.txt
Should return output like this:
Volume ### Ltr Label Fs Type Size Status Info
---------- --- ----------- ----- ---------- ------- --------- --------
Volume 0 E CD-ROM 0 B
Volume 1 F CD-ROM 0 B
Volume 2 G THPS4 CD2 CDFS DVD-ROM 684 MB
Volume 3 D Data NTFS Partition 112 GB Healthy
Volume 4 Partition 38 GB Healthy
Volume 5 C NTFS Partition 93 GB Healthy System
Volume 6 Partition 1907 MB Healthy
Volume 7 Partition 70 GB Healthy
Then you can apply your regex to pull drive letters. Seems kinda like a hassle, but was the best I could find