Here are my specs...
P4 2.4GHZ
768 MB RAM
80 GB HD (Master)
120 GB HD (Slave)
Cable modem
Windows XP Professional
Limewire 4.05 PRO

Now, I don't know if crossing drives is okay with Limewire, but my shared/download folder was originally on my slave drive while Limewire's program directory was on the master. When I re-installed limewire and made the shared/download folder as a subdirectory of limewire on the same drive, my download folder does appear in the library pane. once again, go figure. However, this does not explain my missing mp3's or their .xml dopplegangers. To be honest, it might just be poor file management on my part, but i find it really hard to delete this many files by accident without noticing sooner, and i don't recall ever seeing anything in my recycle bin to prove otherwise.