Uninstalling Anti-virus Software

I have Trend Micro Officescan software installed on my machine (Toshiba notebook PC with Windows XP Professional. My machine was once part of a network domain. Now I want to uninstall Officescan in order to install a new single unit anti-virus program. Officescan however asks for a password as part of their uninstall process. I do not have the password information or any way to obtain the password. Is there a way to get around this problem and uninstall this software without causing serious problems to my computer or operating system.
ever since i unstalled office scane ive had problems icant use my switch user accounts it says disable client services for netware ihave searched and cant find this program my compu. says it does not exsist. My pc is running about half the speed iam having problems with home page toolbars and it willsay iam not connected when iam help also it has problems ending programs and has dumped physical or virtual memorey