Windows shutting down in bootcamp instead of sleeping

I have a problem. whenever i close the lid in windows my macbook pro shuts down. ive checked the power settings and closing the lid ect are set to sleep not shut down. every night i go to sleep i close the lid and the next day i have to power the computer back up. anyone know what might be causing this. specs are 2.66 ghz, 320m nvidia, 250gb hd, 4gb ram.

What happens if you leave the lid up and tell Windows to sleep the MBP? Also, it would help if you told us which version of Windows you're running through Boot Camp?

im running windows 7 professional x64 on my bootcamp partition. i was able to experiment more and just putting it to sleep it wakes up as expected. i think its hibernation is the problem which is different then sleep. my osx version is the osx snow leopard newest version.

Go into the advanced power settings and turn hibernation off. That will also delete the hidden hiberfil.sys file which is created each time.