Damn that makes my eyes hurt, any chance you could get some paragraphs in ?
I am not an expert, but those are varied problems, which could be Software or Hardware related. One of the first places to look usally, would be the RAM, try runnning [URL="http://download.cnet.com/Memtest86/3000-2086_4-10524193.html"]Memtest86[/URL] to see if it finds anything wrong. While your doing that, i am sure the more knowledgeable forum members with offer an alternative.
You bought the PC from [URL="http://www.pcspecialist.co.uk/"]PC Specialist[/URL] then i guess, as you called them ? if its still under warranty, and the guys at PC Specialist couldnt help you over the phone, it maybe worth ringing them up and asking to RMA it back to them to fix it. But this close to Christmas is the worst time, as you may not get it back untill the New Year depending on the problem.
A Motherboard with SATA, can Handle either SATA II or III as they use the same connectors. Sometimes also marked 3.0gbs(sata II) 6.00gbs(sata III). Anyway, i wouldnt worry about SATA III for a regualr HDD as the benfits arent that great, unless your using a Solid state drive (SSD).
Incase you need a new HDD [URL="http://www.overclockers.co.uk/showproduct.php?prodid=HD-082-SA"] This[/URL] will be fine if your looking for a new HDD