I thought I should share what I did to get s3 standby working properly on my machine. My motherboard is an ABIT KN8 Ultra, (BIOS rev12). I didn't end up doing it in this order, but if I had to do it again, this is what I'd do:
1. Unplugged machine, set jumpers to enable USB wakeup on the ports to which the IR transceiver and wireless keyboard/mouse are connected.
2. Rebooted into BIOS and enabled "suspend to s3" and "USB wakeup" in the bios; disabled "wake on" everything else. Saved BIOS and rebooted into windows.
3. Downloaded dumppo.exe and ran "dumppo.exe admin minsleep=s3" and "dumppo.exe admin maxsleep=s3"
4. In "Device Manager" under "Universal Serial Bus controllers," "USB Root Hub," "Power Management" tab, disabled "Allow this device to bring the computer out of standby."
5. In "Device Manager" under "Human Interface Devices," "Microsoft eHome Remote Consumer Controls," disabled "Allow this device to bring the computer out of standby."
6. In "Device Manager" under "Human Interface Devices," "Microsoft eHome Remote Control Keyboard Keys," disabled "Allow this device to bring the computer out of standby."
7. In "Device Manager" under "Network Adapters," "[your network card]," "Power Management" tab, enabled everything.
8. Ran registry hack provided by CrAzY. (first page of this thread). Rebooted.
9. In "Device Manager" under "Human Interface Devices," "Microsoft eHome Remote Consumer Controls," re-enabled "Allow this device to bring the computer out of standby."
10. In "Device Manager" under "Human Interface Devices," "Microsoft eHome Remote Control Keyboard Keys," re-enabled "Allow this device to bring the computer out of standby."
In my case, there were a couple things which sidetracked me. Firstly, upon running "dumppo.exe admin", I could see, even though I installed MCE2005 with "suspend to s3," Windows was set with "minsleep=s1" and "maxsleep=s4," so I changed them both to s3. At that point, after having done everything EXCEPT step 7 above, I was able to put the machine into S3 standby and bring it out using the remote. But the machine was waking itself up between 10 to 60 seconds later, all on its own.
This is where the "Event Viewer" (in Control Panel under "Administrative Tools") came in handy. When I looked at the "System" section of the log, I found there was a "Tcpip" entry which coincided with when the machine was waking itself up. It read, "The system detected that network adapter [my network adapter] was connected to the network, and has initiated normal operation over the network adapter."
On a whim, under the "Power Management" tab for the network adapter, I enabled "Only allow management stations to bring the computer out of standby" and found I was then able to put the machine into S3 - have it stay there - and bring it out with the remote. Hallelujah.
I'm not sure why, even though I had "wake on LAN" disabled in the BIOS, it was waking itself up (a bug, perhaps?), but I do know that was the last setting I changed before it worked perfectly.
Thanks to CrAzY, dancook, juksey, Quicksilver, deadfish and everyone else who posted to this thread.
/b