Here's what to do:
Find FPC.EXE on your computer. The brute force method would be
DIR/S C:\FPC.EXE
Go to the Windoze Control Panel and find System. Under the Advanced settings you should find a PATH variable.
Modify PATH so that it looks like
WHEVER-IT-WAS:C:\WHAT\EVER\DIRECTORY\YOU\FOUND\FPC\IN
Add a ":" and your directory.
Open a NEW windoze DOS window
Do
FPC
If this does not work, type
ECHO $PATH
Make sure it has the directory you wanted is there. If not, a reboot might be in order.