Whenever I put my computer to sleep in vista, it turns on by itself a few minutes. I thought it might be some USB or other peripherals waking the system up, but even when the only thing plugged into this computer is a PS2 keyboard and USB MS mouse, it still does this. Ive gone through the BIOS setup options and everything is set the way it should be.

Changing the sleep mode from STR to normal sleep has no effect. The mobo has the latest BIOS version, and vista has the latest drivers and patches.

Any ideas?

Computer specs:
OS: Windows Vista Business 32 bit SP1
CPU: Athlon64 x2 5600+
Motherboard: Gigabyte GA-M56S-S3 NForce 560 chipset
RAM: 4GB DDR2-800
Video Card: GeForce 8800GT 512MB
HDD's: 320GB WD SATA-II system drive, 250GB seagate IDE drive

Do you have a laser or just a twitchy mouse?
Very high DPI or sensitivity?
If so, only allow a return from sleep via certain keyboard inputs and this may solve your problems.

when the comp is in sleep mode, moving the mouse wont wake it up, nor pressing the keyboard...the only way to wake it up is by pressing the power button, which just quickly brings me back to vista...or i can just leave it alone for a few mins and it will wake up by itself.

Ive just tried unplugging the USB mouse, and using the keyboard, put the machine to sleep...and it still comes on after 30 or so seconds

ive just noticed that it takes exactly 30 seconds before it turns back on.