administrator restrictions/program loss

i started the pC (running XP) up and got ‘chess piece’ instead of my graphic for my user account. When i clicked on it as my account i now get retricted access. 90% of my programs have disappeared from the start ‘all programs’ menu and administrative tools are empty.if i go to ‘all programs/accessories/sytem tools, i just see ‘internet explorer (with no add ons)’ , so no system restore. its like i am running a guest account, but actually i am the administrator. It also ran very very slowly, taking 20 mins per instruction. running chkdsk cleared this up though. no difference in safe mode . ….any ideas?