Won't sleep - just goes back to desktop

I have spent many months with OS X both Leo and Snow. The only piece of advice I can give you is to trawl through Insanelymac forums and learn learn learn. You need to know your system inside out, and be prepared to spend many frustrating hours getting everything to work.
I don't know what your system specs are, but you will find many great guides and knowledgeable people who are willing to help, IF you don't go in with idiotic posts like 'I can't get Snow to install. Any ideas?' type thing.
One thing I will say, is don't try to get everything working from the same drive. Use separate HDD for OS X and Windows. Then you can always boot into either independently.

Sleep Issue

I did all of the above things because I had a sleep issue. After satisfying my self my drivers, bios and settings were ok. I still had the issue. Called up task manager and stared at the processes for a while. Noticed one which would "bump" the system once in a while. (Every two or three mins) I killed the module which was doing it and the problem went away. The software was called up in the boot up and I removed it.

Funnily enough, after solving my problem - as above - my system has started waking up from sleep.
My suspicion is that - similar to you - a process is doing it and the only thing I've changed recently is installing Geniesoft Timeline which does a continuous backup (like time Machine on OS X).
I'm going to disable that before I put my PC to sleep tonight and see what happens.

Sleep problem

Hi if you are still having trouble with sleep mode the answer for me was ridiculously simple although it took me a couple weeks to figure it out. Restart your computer go into the Bios, scroll over to Power, select system suspend, you'll see it's likely on "auto" click on it and change it to the first one in the list - I don't remember what it was called I did it at 4:00am...apparently I couldnt sleep either. Once youv'e saved the changes you should be good to go. Cheers