Win2K server administrator login

The login for the Win2K server left with the last System Administrator. I have access to the hard drive (NTFS). I can read/write/rename/delete files at will. MS-Mail (among other things) is running on the server. Can I use the old NT workaround of deleting/renaming the SAM file,rebooting Win2K and not loose the passwords of users loging on to MS-Mail or otherwise corrupting the Win2K server installation and getting the infamous BSOD? Anyone know of a better way than purchasing commerical software at $200+ to assign a new admin password?