reset

is there a way to completely reset your system and start over from scratch?

Create a new user account that has administrator permissions so you can kill the old one. But don't kill it until you're sure the new one works properly.

If you want you could create two, one as admin and one as a user. Again, you'd use the new admin to kill the old account and to handle your new, regular user account.

to a more extreme level, do a full fresh reinstall from a the system/restore discs

how could i make sure the new admin account works properly?

try installing some apps.