Laptop no longer sleeps when I close the lid

[Solidify]

Sometimes if there are any running applications, such as a web browser, uTorrent etc., it won't ever sleep no matter what the settings are.

This doesn't sound like the issue your having though..you're making it sound more like a hardware problem..

It can't be a hardware problem because the issue only occurred once I changed OS. IT was fine a couple of days ago when I was using Windows 7.