I presume you have some sort of standard client at work, on which you have no priviledges to do anything.
If the computer is running XP then maybe you can try and crack the admin account with a program such as Ophcrack.
Ophcrack is a Windows password cracker based on rainbow tables. (This means it doesn't take hours and hours to run, rather only 20 mins or so).
http://ophcrack.sourceforge.net/
All you do is download the iso image from their website and burn it onto CD. Then, take it to work and try and boot your works PC with the Ophcrack disk.
If this works, then there is a good chance Ophcrack will be able to decipher the password on your admin account (which I presume would solve your problem).
If the BIOS of your works computer is password protected, simply remove the battery on the mother board, wait for a minute and then reinsert it.
Maybe this will work, maybe it won't. At least you can see how well your IT department protects its workstations.
P.S. I presume that the reasons that you can't go into regarding your IT department are that they said "No!"
:-)
P.P.S. This will only work if your workstation is your workstation. If you have a domain based setup at work (where you can login to your account using your user id and password from any station in the building, this won't help I'm afraid).