Almost as annoying as rebooting, but a little faster: you can log out of windows and log back in.

However, if you find you have to reboot anyway, it might be worth the effort to setup a dual boot situation with a little Debian action on another disk/partition. As has been mentioned, you can squeeze quite a bit more hashing performance out of the same hardware and electricity by using GNU/Linux instead of windows. And you'll probably learn a lot in the process