Booting using a start up disk

Hi all:
I have a Desktop machine that looks that was affected by a virus. It is running on Windows XP Home SP2. When it asks for the loggin information seems that is going to access the user profile but at that points it saves the profile and gets back to the signon. I created a startup disk in another machine using drive a and the machine is currently at the does level. Now I want to run a virus program that is installed in the infected machine drive c:\howver, the startup disk does not have the configuration to have the machine recognizing the has a c:\ drive. Is there something I can do at the startup disk config.sys or autoexec.bat to access the drive c: after the machine is at the does command prompt?

Tks