Hard disk not shown

Hello,
i have a maxtor 80 gb SATA hard disk and i cannot acess to it. When ever i connect it to my pc and serch for drives by the option given in disk manager, it detects it but after a few seconds my computer gets restarted. plz help he cz i have a lot of important data in it n need to recover it
if it gets acessable then i will be able to recover my data
PLZ PLZ help.
if u need any more info plz let me know