You're an IT student and you don't know how to fix your own computer?
lol
Ok i guess for you we should keep it basic
1.Defrag it
2.Check startup programs, some manufacturers like apple are arrogant and think the only reason you have a pc is to use iTunes
3.Observe process's.. some you may not use and can be terminated, refer to google if you're unsure what some of them are
4.check your paging file.. too large or too small of an allocation can slow things down...
for example my laptop runs best with it turned off, But my desktop runs best with about 2gig allocated on each HDD
5. try out programs like CCLEANER or TUNEUP UTILITIES
6.Upgrade your RAM or PC
or
7.give more information on the problem and wait for a better reply