My pc crashes frequently

[Vyasram]

Since i reinstalled everything after a virus attack, my pc has been acting strangely I restarts automatically without any warning and it also hard reboots sometimes .When i log into the internet the monitor shows grains of a different pattern each type and everything strucks and i have to hard reboot it again. This problem gets more severe when i install any antivirus suite .It also doesn't allow me to update anything. My system is a Hp havilion 8851 with P3 866,20gb hdd and 192 mb ram. I connect to internet using dial-up and i use winxp.
Please tell me what is the problem and how can i cure it

[shwetanshu]

if u have used repair function of WINDOWS, i think u must perform a full format and not a quick format. if u did format, then uninstall the device drivers and then re-install them. or try installling an antivirus in safe mode and then perform a full system scan in safe mode only. Also check for any unwanted processes and also check for any spywares. Think this should help.

[babumuchhala]

First run an uptodate antivirus scan, and a spyware scan and reeistry mechanics to find all those criminals causing ur system to crash.

Use the PC for 2-3 days to see of everything is fine.

If not then do a Windows reinstall where u format ur HDD. Without which a reinstall is useless.

[gamefreak14]

Telltale signs of a RAM problem. First, goto your BIOS and set ur system to default factory settings. Run XP in safe mode and see if it reoccurs.