[Denhandt]

Certain web sites consistently trigger a system reboot on my home built Windows XP SP3 system, but ONLY when logged on under user accounts. Absolutely no problems if the same web sites are visited while logged on as Administrator. It's been an issue since the build date.

Problem may be narrowed down to web sites with Shockwave Flash Object content: The reboots cease if the Shockwave Flash Object add-in is disabled.

Reboots occur regardless of browser being used (IE, Firefox, etc.), and they occur without creating BSOD messages or error logs. Have tried different sticks of memory. Have uninstalled/reinstalled Flash Player. Have reformated the hard drive and reinstalled XP. Have even used two different hard drives. Only way I've found to eliminate the reboot is to disable the add-in or log in as Administrator. [Temperatures seem fine - consistently <40 C.]

Since the problem persists after OS re-installs using different hard drives, I'm inclined to think it is a hardware problem or conflict (system detailed below, uses as 6 year old 400 watt Antec PSU). Yet, the fact that the problem disappears when logged on as Administrator suggests a software issue.

About ready to give up and re-build with new CPU and/or board. But wondering: Are there obvious troubleshooting techniques that I'm missing?

Tech Support Guy System Info Utility version 1.0.0.1
OS Version: Microsoft Windows XP Professional, Service Pack 3, 32 bit
Processor: AMD Phenom(tm) II X4 965 Processor, x86 Family 16 Model 4 Stepping 3
Processor Count: 4
RAM: 3327 Mb
Graphics Card: ATI Radeon HD 3300 Graphics, 700 Mb
Hard Drives: C: Total - 131068 MB, Free - 46364 MB; D: Total - 131061 MB, Free - 123815 MB; E: Total - 107411 MB, Free - 107209 MB; F: Total - 109998 MB, Free - 103622 MB; G: Total - 115000 MB, Free - 114911 MB; H: Total - 120870 MB, Free - 104102 MB;
Motherboard: BIOSTAR Group, TA790GX A3+, , None
Antivirus: avast! Antivirus, Updated: Yes, On-Demand Scanner: Enabled