If you check my signature below my posts, you will see that is my default system XP Pro SP3 and no issues.
What errors are you getting displayed ?
Can you give more details about your system:
Have (or did) you another Anti-Virus installed in this system, if so what was it and how did you get rid of it ?
What other security based programs do you have installed (antivirus, anti-spy/malware, firewall) ?