Account keeps locking out eventhough NOBODY is logging into it ?????

Hi, on my W2k server we have an account that keeps locking out and I mean roughly every 2 mins. Even though NOBODY apart from mysel or a colleague ever logs in to it. This account will be used every blue moon and will only be done when we are installing a application onto a P.C. according to my server it is not showing up any Virus/spyware has anybody ever come across this. PLEASE HELP its driving me mad.