continuous loading and slow

hi, my comp's running really slow at the moment, it takes ages to load up from bios and yesterday it was running smoothly. i've scanned for spyware, haven't defragged yet but i will soon when i've finished some work here. could there be any other reason for this continuous loading, my loading light on the front won't go out and everything is just...slow!

 

windows xp professional sp2.

i had recently tried to add my new 80 gig drive (posted about it earlier) but my mobo is not capable with it. it might be because i've changed something in the bios but i rebooted and put everything back how it was. a mate of mine said it was most likely the "mydoom" virus but i've scanned it with avg and the symantec tool to remove it and it's not there. i have just defragged both partitions and still it continues to load.

it goes slow as soon as the packard bell logo comes up which is when i turn it on. that stays there for about half a minute and should only be there for 5 seconds. it doesn't appear to be slow just keeps loading something!