I have a 32 bit Windows 7 Lenovo Thinkpad L412. In the past few weeks I have re-imaged my hd to factory state (as I do often). After a few days it begins to go into sleep or stand-by mode after being left idle for around 5-10 minutes. It does not turn off, or actually hibernate, it simply goes to the user log-in screen prompting for a password to return to the desktop. I have no idea why. I am not a noob or anything, I have checked the power options, and power manager and changed all settings for sleep/hibernate/standby to never, including the power plan I am on. I can find absolutely no reason why it is going to the log-in screen. HOWEVER, I think it only starts doing this after I have opened and set-up Windows Media Center for the first time (setting up my tv through a USB tv tuner... which works fine), then comp begins going to sleep after 5-10 minutes indefinitely. It will do this indefinitely, even if I take the PC tuner out or close WMC, or restart. HELP?! This is unbelievably frustrating I cannot believe I can't figure this out.