Windows 7 "hangs" at startup, screen goes black and restarts itself

My acer laptop (acer aspire 5745DG 3D) recently got really slow and laggy. What was more strange is that in task manager it showed 0-9% CPU usage. Then there were more stages that lead it to go wrong.
Anyway, i have removed the hard drive (Western digital blue) and saved all my important data to a separate desktop PC (using a separate cable etc).I have reinstalled windows (7 Ultimate 64bit) on that hard drive using the PC then putting it back in the laptop, but the same problem remains. When i boot windows from the hard drive on the desktop PC the same thing happens (it hangs, goes black and restarts). The warranty for the laptop has expired just a few weeks before it started going wrong and acer support is no use.
My brother, who is quite good with computers, says that i may need to buy a new hard drive but before i do, i thought i might ask you guys.

Thanks for any help or suggestions. :)

You can't count on Win7 to start when moved to different hardware without SysPrep to move HD to another computer.

I'd instead try booting the Win7 installer for the licensed version on the Acer to Clean Reinstall - Factory OEM Windows 7.

If it fails test the HD using maker's HD Diagnostic extended CD scan followed by Disk Check run from installer System Recovery Options Command Line, on a full disk partition created in installer or using Step 2.2 here: SSD - HDD Optimize for Windows Reinstallation.

Check for newer BIOS update. If none reset BIOS to defaults, set SATA controller to AHCI to try install. Clear CMOS - 3 Ways to Clear the CMOS - Reset BIOS

Test your RAM - Test with Memtest86+ for 5-6 passes. Remove all but 2gb RAM to try install, swap RAM sticks, check for debris in slots.

Thank you, i will try all of those.
Also i forgot to mention that when running the Windows 7 (ultimate 64bit) installer disk from the optical drive on the laptop, it asks for drivers.
So my brother said that he will try to install windows xp 64bit version (with the laptop's disk drive) because that won't ask for drivers. That did not work either.

Thank you again for the quick reply.

Where did you get Ultimate version for your Acer? Did it come preinstalled? What is the licensed version on COA sticker attached to machine?

If installer requests drivers it is normally a problem with the installer ISO, burn or write to stick.

the laptop had home premium 64bit preinstalled in it, but my brother said he only has the installer disk for ultimate so we decided to use that (although its just a plain, colourless disk so im guessing its not a licensed copy) (it might be outdated?)

Use the installer for your licensed version which I linked earlier, follow the steps to reinstall with Product Key on COA sticker.

I'm his brother, it's a licensed DVD it's got all the latest updates.