Computer sluggish, freezing alot

Hi, I had a problem a while ago with Ulead and i managed to fix it by changing my codecs but now i have another problem!

My computer is really slow, and now is freezing frequently, during using MovieFactory, Nero, or Playing Video Files, along with other things.

Anyway, I have Ram Idle installed telling me i have 232 RAM, And my drive temperatures are 38C each, so its not a RAM issue or an Overheating thing.

I also have AVG Anti Virus, and Erely Detection Center installed, and have no Spy ware or Viruses.

All extra functions are turned off start-up by msconfig, and I ran that memcheck thing, and I fixed the errors I had.

Any tips or clues on how I can fix this?

Any help, no matter how small would be really good.

When did you last defrag the HDD?