Maybe its nothing to serious. Have you done the basic things before you attempt to format and re-install or run the recovery disc.
If i was you i would first boot up into safe mode, run disc cleanup, run disc defragmenter.
reboot into Safe mode with networking download AVG and CCleaner (crap cleaner) and finally grab a copy of spybot search and destroy install the three programs and update them, run ccleaner, run spybot and finally run avg.
Was anything found out of the ordinary if so where they all fixed up?
If there where alot of problems found i would then suggest trying a normal boot again and see what happens, if it hangs it maybe a driver issue, or registry issue, also what start up items did you untick? And whats still available?