gxd135,
.tmp files are more than likely some sort of system file. AutoCAD files you can safely delete (when AutoCAD is NOT running), acadstk.dmp, acad.err, *.AC$, and *.log - be carefull here though, you don't want to delete any system log files.
Not that you asked, but whenever I either install or customize AutoCAD, I create two directories directly underneath the AutoCAD install directory ie., C:\Program Files\Autodesk Architectural Desktop 3.3\, called AcadTemp and BatchLogFiles. Then I direct AutoCAD to locate all temporary drawing files, autosave files, and temporary X-refs to the AcadTemp directory. If I'm using logfilemode, I'll set the logfilepath to the BatchLogFiles path (usually because I'm batch processing files). This way when AutoCAD crashes, I've only got a handfull of places to clean up, and if the computer starts acting sluggish, I'll close AutoCAD and delete everything in these directories including the UNDO file AutoCAD creates, and usually see the performance come back to where it was.
HTH
Todd