windows xp won't boot after installing Update

I have system with 2.6GHz, dual-core,1gb memory. It's running very smoothly.
i just formatted my pc with Xp sp2.I installed basics, mozilla, yahoo and msn messenger a firewall and Malwarebytes.Everything was fine for a while,last couple days I had a list of security updates that was asking to install.I tried them and they failed, and then when I went to reboot it gave me the safe mode option... when I tried that it would just switch off and reboot again, continuosly. I then used the Boot in last known working configuration option and it booted up ok, still had errors installing updates. Sometime it show's screen just goes black and get a "no monitor signal message" . What should i do?? can you help me out???

Try system restore, which reinstall the files to how they were before the update occured. Check with your ram , Open your pc.. Remove the ram, and Place it back in. The computer keeps on freezing becuase the Memory ram is pilleed up with some virus, So you might want to either, Reboot your computer, or Upgrade the ram. Rebooting your system press F8, then choose "Start Windows in safe mode with comand prompt". In the comand prompt just write in %systemroot%\system32\restore\rstrui.exe. If you have windows XP, it should be the same. You can try to start the WinXP Setup CD and choose repair, when comandpromt appears just type in this line "%systemroot%\system32\restore\rstrui.exe" without brackets. If above doesn't work then you should go for fresh installation.

This problem is always occured with XP an it's on the chipset, motherboard , BIOS version, and CPU.You should do the following. Go in BIOS setup,an disable the L1 and L2 cache.Boot the problem computer with an alternative OS or to the safe mode command line if possible. Assuming you can get to the Windows directory on the boot partition, navigate to this file and change its name so that it does not load the next time the machine is booted:
windows\system32\drivers\update.sys
If this will not work then the only option is you have to reinstall your operating system.