Apparently random BSODs

Hi,
Can anyone offer any advice on the following problem please?

I have had this PC for a couple of years now and it has never been particularly reliable. When I first had it ii used to suffer frequent screen black-outs for a couple of seconds and then sometimes come back OK, sometimes come back with the colours corrupted, and sometimes crash completely.

I resorted to a paying a local "expert" to fix it who suggested it was virus related and that I upgrade from MS Essentials to Kaspersky. So I bought Kaspersky and it flatly refused to install and no explanation could ever be found.

I persevered on with it and seemed to have fixed the graphics problem by adding a video adapter, rather than rely on the onboard graphics. However, I still had lots of crashes and loads of things within Windows stopped working (e.g. back-up and restore, windows update etc.).

So, just before Christmas, I bit the bullet and did a complete Windows 7 re-install (I don't have disk - there was an option to re-install in one of the boot up menus).

Hey presto - everything seemed fine. Full Windows functionality was restored, Kaspersky installed correctly, and everything was fine. For about a week. Then the BSOD's started happening again.

These seem to be random. Some days the PC will run all day without crashing. Others it will crash during boot up.

I have run HDTune diagnostics on the hard drive and it appears to be fine (both scanning and healthcheck statistics). I have run Windows memory test and it doesn't report anything.

I have tried something called "whocrashed" but it always seems to say the problem is related to an unidentified driver.

I have kept my Windows 7 up to date since re-installing it.

Any help would be greatly appreciated!

Thanks

Dave

Anyone able to help? Any more information needed from me?

Really would appreciate some help if some kind soul could look at this for me!

Thanks

Dave

Anyone able to help? if not, any suggestions as to where else to seek help?

Thanks

Dave