You can use runas to run a program as an Administrator while still logged on as the user (providing you can get to the Run command or a command prompt).
The syntax is:
runas /u:domainname\username programyouwanttorun.exe
A good idea is to launch the command crompt, as from there you can run other programs (and control panel applets in XP) as you wish.
To do so with an admin account called admin123 on a domain called domain789 the syntax is:
runas /u:domain789\admin123 cmd.exe