if you need to switch monitors too, you might consider windows remote desktop, if you only need to switch keyboard and mouse you may consider synergy http://synergy2.sourceforge.net/
both free and easy. I use both these and also have a kvm switch and i still usually use remote desktop into the other box on the kvm. if your monitors are dvi, those kvms are a little pricey.
do you need video switching too? or only keyboard and mouse.
If only keyboard/mouse, try the below. I have been using it for about 6 months now, works flawlessly. It's free and you dont have to deal with all the extra cables that's required by a kvm box.
