From an administrative command prompt, type 'powercfg -h off' to get that space back. Plus, I have 8 gigs of RAM, and hibernation uses as much disk space as you have RAM. The only thing, again is that you can't uninstall SP1. If you select yes, you'll get back around 2 to 3 gigs. Next, type 'vsp1cln' at the command prompt. That means, click the Start Menu, type cmd.exe, then right-click on it and click 'Run as Administrator.' Alternatively, you can press Ctrl-Shift-Enter to run something as Administrator. Open up an administrative command prompt.
After a few months with the Service Pack, I've decided for myself that it's a good thing and decided I don't need the option.
I've got a smallish C: drive, about 140G, but noticed that in the last week or so I'd had only 200megs free.
