Yes you can delete them as it was explained to me, these are temporary (and potentially annoying) files - the ones that are numbered, that is. This is a bug I recently reported and SW recently fixed in the latest service pack. Here is the communication from Dassault:
-------- Original Message --------
Subject: SolidWorks SPR Status change notification
Date: 9 Mar 2010 05:55:17 -0500
The following SPR (SolidWorks Performance Report) status has changed to Implemented.
SR# (Service Request): 1-1455166681
VAR SR#: 15164
Description: Solver writes large temporary files with numerical extension (..096, .097, .098 ... .123, .124, etc) to 'Last User path' folder and never deletes them
Version: 2010 SP02
For more information, visit the VAR Resource Center and select Service Requests (SRs) or Knowledge Base (SPRs).
Dassault Systèmes SolidWorks Corp. Technical Support
I can confirm that all *.096 - *.127 files can be deleted. Also *.PC0, *.PC1, *.P39, *.P41, *.P45.
I was just able to clean up about 10 Gigs of space by deleting them all.
Glad you looked into the simulation temp files.
We're running 2010 SP3.1 and those temporary *.NUM files still show up inconsistently under the SW install directory. Although the majority of the time those files do disappear automagically, it seems the software fix still needs some tweaking.
Did you find anything about the *.EFF files? As you said, there are a plethora of simulation files in the results folders (including empty folders!) so it would be benefical to know which files may be safely deleted.
Thanks for posting this issue up!