Windows 8 Freezes Totally When Left Idle?

Basically about 1 month ago a good friend of mine purchased a brand new acer desktop computer, I haven't got the exact model to hand as he lives 200 kilometers from me and he's not tech savvy at all, however, from what I remember of it, it's windows 8 x64, 4gb ram and i3 processor, so not bad at all.

When he got it I set it up for him as in just put in the regional setting etc.. and ran through the initial set up and all went well. I installed all his programs and all was good.

So about a month on he rang me and said his computer is just freezing randomly always when it's left idle for 10 minutes or so and this happens all day every day.

..... Ran hitman pro which said all was clean.
.....Ran chkdsk /f which was fine
.....Went into power options and set both screen and sleep to never
....Ran sfc /scannow which said it found some corrupt file but could not fix all (ran this from command prompt from inside windows as admin)
...Tried a system restore to the 14th of this month but said it couldn't do it as it may be corrupt but it let do a restore to a later date but still the same issue.

This is only a new pc, so if I can't sort the problem rather than doing a fresh install and checking all the hardware internally I'm wondering if he should bring it back to the shop as it's only a month old, or would I be better of doing the fresh install ?