A few generic suggestions as I never encountered this particular problem.
1) Never seen personal settings completely vanish (which doesn't mean it can't happen, though). So your desktop settings and all other things should be somewhere. Did you try all accounts shown on the welcome screen yet? Did you check the Documents and Settings folder for an "orphaned" folder that might be yours?
2) Assuming you find an account that seems to be yours, make it an admin account again and remove the password (if any) from the account.
3) Remove all the "useless" accounts just keeping yours and after a reboot the welcome screen should no longer appear.
Of course there are a number of scenarios where 2 and 3 might get you in trouble so please be careful.
Possibly a simpler solution: Do you happen to have a system restore point before the driver install that might be convenient to use?
In any case: Good luck! (And sorry if the suggestions are way too obvious)