Windows XP always boots up in safemode what is the fix?

Dear TeckRepublic members. Please could you advise how I can correct a problem that has just developed on my PC running XP. The computer now only boots uo in safemode at switch on and I cannot get it to load normaly. It also refuses to roll back on system restore even though there are lots of restore points showing. I have done a full scan with AVG full addition and AVG reports no virus found.
Any advice would be really appreciated.

Kind regards
Glyn