if u r on XP, (other O/S or IE versions might have different location of this)
open IE, go to tools > Internet options, click Programs tab, and at the bottom you'll see a checkbox (mentioning that to see weather IE is default browser or not),
just click it checked, and next toime you'll open IE<it'll be default.
again repeating other's responce:
WHY DID YOU REMOVED MOZILLA??
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"