Turning the pc on without the fan attached after just purchasing a brand new AMD 1600 XP

One great classic one is allowing cabrone to install winxp on my computer. I have 2 separate hard drives that up until my third format of winxp hadn't been partitioned. He was messing around in 'fdisk' seeing which partition he had to format and, as always, BLAZING through warning screens and selection screens with incredible speed. I ended up with a win98 hd and a winxp hd because he deleted the second hard drive holding all of the important stuff i saved off of my win98 partition.

Dumbest thing i've done personally...Somehow I messed up my hard drive so badly that when I turned on my computer it would say 'remove system disk' as if i had a floppy disk in the computer only there wasn't one. I think i had to write 0s to fix that problem.