Memory resident anti-virus/spyware programs?

[d000hg]

I am aware that many AV programs include the ability to constantly run in the background - but this slows things down. I recently took this off a P41.7GHz PC and it now boots quickly, not slower than my 700MHz machine.

Does anti-spyware software normally run all the time or do you perform a scan? My older PIII PC cannot take anything running in memory since it's not exactly that fast already!

[PIPER]

Most will run in the backround once you do the install unless you remove them from startup....question is, do you want to do the scan each time you boot or do them at the times you choose....unless your using an email program on your system vs. web based mail...scanning at your leisure should be ok unless you do a lot of surfing...in which case I would suggest you turn it on after you boot...the spyware program, same thing...leave it out of the startup and turn it on before you go surfing. You will need to manage your startup with a third party app if I am not mistaken because once you turn it on windows will put it back into the startup automatically.....JMHO.