Windows 7: Weird phantom inputs

sometimes, at random times, it seems like my computer reads an input of Alt without me touching it. it happens a lot when i am typing which makes it so that when i hit they next key while i am typing i am entering into a menu or going back to a previous web page, loosing all i typed. i thought it was the previous keyboard that was doing this but i changed the keyboard and it still happens. the keyboard i am now using is a microsoft branded one, so i do not think it is the keyboard necessarily right now. it seems to be the OS but i have no idea what could be forcing this to happen. is there a way to fix this or am i destined to go through this crap forever? if it helps, i am using a custom built computer with Home Premium. i am using the Microsoft Wireless Keyboard 3000 bundle.