This is mostly just a follow-up, but I have a question too. My problem is gone. I did all of the things recommended here. I popped open the case and blew everything out. Oddly enough, my 120mm case fan had become disconnected. This took care of the reboot problem. I still had problems with CS:S locking up occasionally, I uninstalled/reinstalled drivers, and did a clean install of Steam and that did the trick.
Now, heres the question. ZD was complaining about registration again (doh!), and the subject came up about monitors, FPS, etc. My FPS is still incredibly low; I'm usually between 30 and 50. Is it mostly just that my system is old -- so just all around weak? Or is there possibly a weak link in my current hardware? Besides the hardware listed above, I have an ACER LCD -- 16 ms response. Honestly, are there any LCDs that would give a decent response -- like if I upgraded to one of those fancy 2 ms response LCD monitors? Or should I wait for an OLED monitor?
Please edumacate me.