Unusual, Unprompted Wake-ups

Hello, I've been perusing the forums and have gotten some great info for my transition from XP to Windows 7 but am having what seems to be a unique problem, hence this thread.

Since installing Windows 7 (64) on a fresh new HD my computer's been waking itself up from sleep mode fairly often (every hour or two, maybe). I've gone through all the other threads on this subject and tried most of the fixes I found (disallowing ethernet wake-ups e.g.) to no avail. What's particularly disconcerting about these wake-ups is they produce a strange 'clunk' sound and my power LED flashes. The cmd window tells me my keyboard is the device waking the machine up but I don't know if I believe it.

Does anyone have any inkling as to what this might be? I'm suspicious of my floppy drive (yeah, I know) as it makes similar sounding grumblings on start-up. Thanks in advance for any help.

Jonathan and Rich, thanks but those were both among the fixes I've already tried.

Thanks for the FAQ Brink, I'll give it a gander when (or if) I get my homework done tonight.

-Sam

Disable power options in your BIOS. This will stop devices such as keyboard or something else waking up the PC.

Thanks Frostmourne, I'll try that. I'll still be able to wake it up with a keystroke when I want to though, right? Also, I just want to note that the 'clunk' sound I hear during these wake-ups doesn't happen when I manually wake the computer up with a mouse wiggle or keystroke.

This depends on your motherboard - it should have a number of options, such as S3 sleep, along with wake options.

I looked at my BIOS and all devices were disabled under the power tab. Going through Brink's FAQ now.