How can I find out which standby/sleep mode I'm under (S1, S2 or S3) when on Windows 7? My BIOS does not have such a setting.
S2 never really existed. S1 was a basically useless state that didn't really save any power but did not require added hardware to support. You can tell if your system is using it when in standby because all of the fans and such do not shut off. If the system generally appears to have turned off when you suspend, then it's S3.