Solidworks 2001 SP7
1) run regedit and find this key: 
HKEY_LOCAL_MACHINE\Solidworks\Security 
this is for Windows2000 might be diferent base name for Win98 or WinNT 
 
2) Edit the following here: 
S/N: 9940 0999 8888 7713 
Lightworks: 9940 1999 8888 2261 
Featureworks: 1011 0188 1286 5111 
 
SolidWorks Animator: 0747 0328 0074 0474 
SolidWorks Moldbase: 0129 0110 0448 0072 
SolidWorks Piping: 0992 0056 0577 0368 
SolidWorks Toolbox: 0846 0859 0017 0845 
 
3) Run solidworks, you will be prompted for an authentication code enter: W45G