Something is shutting off my services

I'm running Win XP SP3. I bought a new computer a few months ago and three or four times since I installed my Win XP O.S. several important services have been turned off. I thought at first it was caused by malware, but since then I clean out all spyware and malware daily and it has still happened. Any suggestions as to why? Thank you.

 

The services that are being shut off are my anti-virus program (Symantec - Endpoint Protection) and all of its parts, Spyware Doctor and all of its parts, Diskkeeper, my SpamFighter program and ZoneAlarm. It only seems to shut down security programs but not all of them. It leaves Spybot alone and SuperAntiSpyware.

Only once, after I have turned them back on and run an anti-virus program have I found a couple of downloader trojans. Other times I have found nothing but ordinary spyware.

 

I'm sorry, I forgot to answer your question. No, a simple re-boot doesn't rstore the shut off programs.