I game a lot and I do not want it slowed down. It has 1gb ram, 1.8ghz celeron cpu, and a 256mb ram video card.

As my computer was running abnormally I called HP customer care. The agent advised me to run the virus scan in the safe mode. More than once I tried running the Kaspersky Virus scan, but my computer shuts down after some time without any warning. Sometime it shuts down after 20% of the scan or sometime after 80%.
What might you think is the problem and how could I resolve it?

do u think kaspersky was a good choice for an antivirus? should i change it?
is it still effective eventhough there is a newer version out already?
does kaspersky antivirus v6 protect the PC from other malicious programs like adware, spyware and the like or it only protects the computer from viruses? cos i downloaded spyware doctor, should i just unintstall spyware doc.?