Motherboard Problems

If you have a more recent motherboard it may have a related diagnostics utility available from your friendly m-board manufacturer.

http://www.asus.com.tw/download/mbdriver/mb-utility.htm

http://www.intel.com/design/software/drivers/index.htm?iid=ipp_nav+soft_btn&

Some of the symptoms are: Memory error messages during the POST, can't see hard drive(s), BIOS resets to the default, memory reads more or less than what you have in the machine.

Maintanence: Make sure you keep the machine free of dust, check to see if all cards and chips are seated properly, check to make sure fans are working.

way too many symptoms are available for you...

anything could happen... if you'd instead post

1) os
2) system specs (with brand names too pls)
3) symptoms you *ARE* seeing

everyone may be a bit more helpful

Example:

me: My car rattles.
mechanic: when?
me: all the time
mechanic: is this with the engine running? not running? while driving? etc etc etc..

(not trying to be an ass but sometimes posting *its broke* doesn't really help)