Crashing/coloured spots flashing

[PokerGuy]

Having major issues with my iMac (i7) which is about 4-5 years old.

It keeps randomly crashing/freezing and also I am getting large groups of flashing and static blocks of coloured spots - I have uploaded a short video of an example here:

http://www.youtube.com/watch?v=qaXyqCtC4Dw&feature=youtu.be

Anyone have any ideas what I should do? Is it likely to be hardware or software problem? Would a factory reset stand some chance of resolving it?

Any help much appreciated, as always

 

[Diversion]

Looks like the GPU (graphics) are going out.. What GPU does it have? First thing i'd try is a full wipe and reinstall of OSX. If that doesn't work, i'd take it into Apple to get a quote to have it fixed. I would hope they wouldn't charge you for a full logic board.. not sure if the GPU by itself is replaceable.

 

[PokerGuy]

Looks like the GPU (graphics) are going out.. What GPU does it have? First thing i'd try is a full wipe and reinstall of OSX. If that doesn't work, i'd take it into Apple to get a quote to have it fixed. I would hope they wouldn't charge you for a full logic board.. not sure if the GPU by itself is replaceable.

Thanks for your reply - it has ATI Radeon HD 5750 1024 MB

I am going to try the complete reinstall - I haven't ever done one on a mac (which I guess shows how great they are overall - I remember doing them every few months back on my PCs) - is it pretty straightforward? Is there a simple tutorial that would show me how to do it?