I've been using Ultramon for years and can't see going without it - or dual monitors. Unfortunately it is not free. I never had any problems running it on this 64-bit Win7 system. My only complaint is that it does not correct Window's deficiency to allow a second Quicklaunch bar on the 2nd monitor. Oh well.
BTW, for those running with two monitors, Link Removed has some really cool dual background images for dual-monitor setups.