i have just finished building my pc and its now up and running on XP pro....couldnt get hold of a copy of vista....yet

i have a little cash in my paypal...and was wondering what people suggest i buy for my pc...any must have items out there. its not a gaming pc, its for music and internet etc....it has at the minute, 500gb HD on board graphics and sound all in a media centre case. i only has 1 pci slot left so consider this

cheers guys. what should i spend my money on???