When in standby, the computer is completely silent - no fan, no hard disk drive noise, no video. Just a blinking power light. Which is what I expect.
When I press the power button to wake up the computer, I hear the fans kick on, the hard drives spin up, but there is no video. I've set the BIOS to run VGA POST after S3 Standby resume, and I do see a one line message on the monitor indicating that happened, but no Windows desktop appears. There's no video at all.
After power on, I can do things like open the open the CD rom tray and see disk activity occur. Same with inserting a floppy. But I try pinging the PC from a Mac on the same network and it doesn't respond.
Along with this problem. this PC has a narcolepsy issue. Even though I set the Power Option set to *never* go into standby mode, every once in a while, the machine will suddenly go to standby mode, and once there, it's as good as having shutdown. And when it goes into standby mode, the system is not being stressed - usually IE and/or Word is running.
Machine details: Windows XP Pro (SP2). Asus P4C800 deluxe motherboard. intel P4 3.0 Ghz, ATI All in wonder 9600XT graphics card. 2 IDE hard drives, and 1 sata drive. a DVD drive, ZIP drive. Enermax Noisetaker 425W power supply. Assembled by Monarch computer almost 3 years ago. I've run several virus checks (AOL Active virus shield, Windows Defender, onlne House Call), and adware check (SpyBot S&D) all clean.
I've run Prime95 for a few hours to check if it was a CPU related issue, but the system ran fine without suddenly going into standby. I've run a video card stress test for 2 hours and there were no problems. Ran Memtest86+ for several hours, (booting from the Ultimate Boot CD) no problems.
Could this be a power supply issue? We did add a SATA drive several months prior to when this problem started to occur, so could the power supply be on the brink of being overstressed? Or could this be a video card issue? Or could this be a software issue?
Advanced thanks for any suggestions on what else I can do to narrow down the cause of this problem.