Computer does not boot up

This maybe because of BIOS error or change in BIOS setup,maybe you have tried overclocking on of PC's component.or maybe a faulty hard disk.the best way is to open the case and remove battery of motherboard and wait for 20 seconds and then put the battery in place and check cable connections and make sure they are fastened. but befire touching anything in PC get rid of your hands static charge by touching metal pipes or window metal frame or if you can wear anti-static charge gloves.change the BIOS to default setting by just pressing F2 or whatever is written when you boot and in setup just select default setting and save and exit. I am repeating try removing battery for 20 seconds. it really works for lots of problems.

The best solution is for you to check your memory stick on the motherboard . remove by pressing aside the two clip sideways and the memory stick fly out from its socket then put it back on the slot writing one (1) so as to verify the stick then re-ON the system if it doesn't then change the memory to a good one and test it back ok.if it didn't work out re post the problem ok.