My pc doesnt boot up

I would check the voltage (115) on the back on the computer and i would insert restorer CD for XP find NTLDR and replace the file

Troubleshooting this problem can be difficult,so check the obvious

Are you getting power from power supply,can you hear the fan,also listen to the cpu fan

Check the Memory slots to make sure that memory is seated properly and memory is of the same type and not mixed

Check another graphics card to see if this causes the screen to be blank

Boot computer,as startup screen appears press the designated key to enter bios setup,check that drives are being detected and the boot order is correct

I would suggest after checking the system,to reload the system files by reinstalling the operating system

the ntldr error may be because your disk is highly fragmented. see if simply putting your installation cd in the drive is enuf to get it to boot. it may go to the cd to look for ntldr. if this works to get you up, defrag immediately. you can try replacing ntldr but probably it will not help

Try to have your pc boot in a floppy disk and then once you have the A: prompt just type in fdisk /mbr. So you'll have like this
A:\>fdisk /mbr and hit enter. Note that on the boot disk be sure you have this "Fdisk" file otherwise it will give you an error. "Bad Command Error". Try this and good luck.