Have you tried running either memtest or orthos with your system yet? It's quite possible ram would work in your mate's system but not your own (and applications not being able to install without errors really does suggest ram or a bad connection between your hdd and motherboard).
Just by way of example. I had an older system which was throwing errors up all over the place and it turned out it was the RAM (even though both sticks worked 100% perfectly alone). The motherboard had 3 slots for ram, and of all the possible positions they could be populated with 2 sticks, only one position would enable my system to make it through memtest without giving errors.
Just by way of example. I had an older system which was throwing errors up all over the place and it turned out it was the RAM (even though both sticks worked 100% perfectly alone). The motherboard had 3 slots for ram, and of all the possible positions they could be populated with 2 sticks, only one position would enable my system to make it through memtest without giving errors.