Try using hibernate, or upgrade to XP home..
The guidelines for power usage in STR (S3/Standby) calls for the PC to be roughly using 20% of its typical power. So if you have a 100w pc, STR is still using a sizable amount of power (hence its refered to as light sleep). And even if you have a dimunitive 50w pc, you'd still be drawing .8a. S4 (STD/Hibernate) uses much less, but takes much longer too boot back up.
My understanding with STR is that the only power left is just enough to keep the ram refreshed, everything else is dead. In this case the power draw is probably only a few watts if that.
Once I get my setup finished with my new DC-DC power supply I will be testing how long I can stay in STR because I use my only once a week, if that.
I'd investigate hibernation too - you should be able to do this with Win2K.
You can set your machine to STR after a certain time, then have the machine wake and hibernate after a period of time in STR state.
Whether you can trigger the hibernate following STR without going into STR through a timeout, I don't know, but it's worth a play
Hibernate serialises your memory and state to disc, and takes zero power. All that'll be running is your +5V standby line, which draws next to bugger all.
Boot time for me from hibernated takes around 20 seconds.
Hibernate/S4/STD "boot" times can wildly vary. I think I was looking at 30+ seconds when I played with it breifly on a duron 750 and 512 ram. It depends heavily on how much ram you have, and how quick your hd is. It can also take a while to hibernate, as it writes however much ram you have to disk.