Acer Extensa

So, I had a problem with my friend's laptop, she gave it to me, saying that it won't load after login. I tried to enter BIOS with Alt+F10, but after that, the laptop wouldn't go past Acer logo. I thought that it would be good to use my desktop to install Windows 7 on laptop's hard drive. But...

I was forced recently to re-install Windows 7 after some problems arose thant I could not fix . The laptop is an Acer Extensa 5620 , rather old now but still functioning . After reinstalling ( this time I changed to 64 bit ) it was working very well . Now it keeps going into sleep mode . ODDLY...