all good advice listed so far. another thing to consider would possibly be how full your hard drive is and how much RAM you have. to know how much ram, right click my computer icon and click properties. to know how full the hard drive is, open my computer and right click the c drive and click properties. a hard drive that is almost full and/or insufficient RMA could cause "slowness". spyware-busting software tool, and defrag could also help for sure.

if you frequent the naughty websites, slowness should be expected :-) even if not, still a good anti-virus software tool should ALWAYS be used.

let us know what you find out and what fixed it, or if you still need some more help

good luck!