Acer aspire 5520 problems

Hi basically i baught a new hdd as my old ended up with a broke hdd drive and i loaded vista on and it was fine then basically laptop started not turning on and just gave me a nvidia cable unplugged message over and over again the hdd drive was not even a month old it is a 320gb hitachi i believe.

The laptop does turn on if you try and try but take ages and is painfully slow but shouldnt be as it isnt that low spec tbh

it has 3bg ram
2.something pentium processor
320gb 7200rpm hdd

has about 30gb of stuff and thats it.

would really very much appreciate the help as i use this to store my car club info on and i dont want to loose anything.

next boot ill try and copy the error message down


cheers

mick