Help vista boot up probelm

Hello,
my vista on boot up takes ages so swiitch off it come up systom restore.it goes in to this for ages the conme up see your dealer.i swtich it off again then on it boots up.i have taken it back so many times> i feel systom restore not working
.and the boot up is so slow. i did go into the Bios and put all back to default.. still not working.i do not know where it is booting from..... so i swtich on it takes....30 min or more to boot up. ad when it comes on i take it back to april or before..still no good i do not have a repair CD as it is from dell it is a tower computer i do have a disck which i can reload vista... but i do not want to do that.On the disck there is no vista repair. itjusat said load vista/thank u