You dont have to fold 24/7. You can just have it run while you have the PC on. It has a tray icon that you see to let you know it is working, but other than that you dont see much of it as it does run in the background.
It runs fine in Win7. I am running it on Win7 64 Bit right now. Using the GPU folding on my 8800GTS.
The 2 main things to remember:
1. Turn it off if you are going to game.
2. Use F@HMon to check the status of the WU. They have a preferred time date for completion. If a WU is not completed in that time it is basically lost from what i know. So try to make sure that you have the machine on long enough to finish the WU you had started.
Most WU have several days for a final deadline though. so it shouldnt be to hard to complete the WU in that time frame. It all depends on the WU being folded at the time. Right now my WU has a preferred deadline in 2 days but a final deadline in 5 days. I will be done with it in just under 3 hours. So there is plenty of time to get a Wu done if you dont fold 24/7.