Uninstall the game from the Add/Remove programs. After that is done, delete the FIFA 07 folder in your EA SPORTS folder. Then go to My Documents and delete the FIFA 07 folder there.
Lastly, you need to delete the FIFA 07 key in the registry. To do this, you must be really careful because if you do something wrong with the registry, you might screw up your whole computer.
Anyway, go to Start>run and type in
regedit
Now, go here. HKEY_LOCAL_MACHINE\SOFTWARE\EA SPORTS
and delete the FIFA 07 tree. If FIFA is the only EA Sports game that you have got, then delete the EA Sports tree and the EA Sports folder in C
Program Files.
When does this crash happen? There may be a MUCH easier solution.
If it crashes when a match is loading, you only have to do the following. In CM07, go to Tools|Regenerate fat and bh files. After you have done that, delete your FIFA 07 folder from the My Documents folder. That is the best way to ensure that the changes have been made. Alternatively, you can start the game, and go to Team Management>Reset My Squads. That should take care of it as well, if you don't want to delete the My Documents>FIFA 07 folder.