I4one

Your issue seems to be OS related and the chunky mouse effect is just the symptoms...
Explorer usually occurs as one instance only - however XP has many hidden limitations that aren't discussed much...and I can't recall them all - but one has to do with a limitation on the amt of SubDirectories and perhaps "depth" (8 deep) available from Root C:\
e.g (C:\Documents and Settings\Zemo\4th\5th\6th\7th\8th - you get the idea)

Also - If there are DualCore (X2 -or Intel D) that might explain the multiple occurences of Explorer - but I just don't know.

Try this too;
Start | Run REGSVR32 /u SHMEDIA.DLL
this is the file that WIn uses to roganizze and index and associate Media files with thumbnails and Players, etc

This is totally reversible and un-doable
Start | RUn REGSVR32 /i SHMEDIA.DLL

Also Sometimes the XP Media DIRs can have a Corrupt Thumbsvw.dll - or Desktop.ini File