won't boot.

hi all,hope you can help,ok my problem is......last night with out any warning my pc just turned itself off,it re-started itself but just hung at the windows loading up screen so i turned it off at the power button,left it a few minutes then turned it back on,but now its just stuck in a loop of dell startup screen,choose operating system,windows startup screen then back to the begining,it won't even start up in safe mode.
now i've had a feeling for a few weeks that it was on its last legs due to a massive drop in performance and numerous errors,have my fears been confirmed?
thanks for any help or advice given.

 

hi,thanks for the quick responce and welcome,i ran a harddrive test and mem test the other day and everything came back fine,i can't get into my pc at the minute to re-run the tests as its not responding at all.