Blue Screen

Have a look in event viewer,(stsrt, right click computer, click manage, click event viewer- look for any warning ings/errors .

Have you had driver updates for the graphics ?- can be rolled back, if you have-same as above. but click device manager and look for exclamation on a device.

Although it seems this has on board graphics- if it has a graphics card installed, it would be worth removing it and connecting to the graphics port on the on board graphics- this will eliminate the graphics card, if you have one.

if going inside your pc- Take care to turn off at the mains, and press the start button and this will drain the system. Touch a radiator or metal service pie to earth yourself to avoid introducing static.

Also , it can be worth removing, and reseating the ram, as sometimes problems can be sorted by that simple operation

If you cannot get into Windows

Try to get the error number when the blue screen comes up- then  this link to error codes might help.

 http://msdn.microsoft.com/en-us/library/ms681381%28VS.85%29.aspx

Trouble shoting from page 50- 70 might help

http://support.acer.com/acerpanam/Manuals/acer/2011/ServiceGuides/SG_ASX3812_X5812_BOOK.pdf

I have looked around, and without the numbers off the motherboard, it is hard to find a replacement- I would write down all number tags on the motherboard, then try googling for it- might have difficulty because of the age of the pc, like I found when looking for you.