Random BSODs with NEW Hi-Spec PC

Hi guys,
I really hope you can help with this. I occasionally keep getting BSODs with different messages (some related to fastfat.sys) and don't really know what to do.
My PC initially had an ASUS A8N-SLI Deluxe but the PC manufacturer have changed it for an ABIT AN8 32X as the layout of the ASUS meant I couldn't add a further PCI card (belkin wifi pre-N). Also I did get a BSOD or two with the ASUS so thought that a different board might help - it hasn't :-(
I presume that the same RAM has been used in both systems (CORSAIR 2 x 1GB PC3500LLPRO). The other specs of my PC is in my user profile.
I don't really want to box up the PC again and send it back to the manufacturer as I feel things are a bit vague as to what's wrong with it although they've been very helpful to date. If you could help point me in the right direction I could perhaps pursue this further.
Attached is a zip with the 8 minidumps created to date.
Thanks in advance for any advice.
Regards,
Lee
PS: I forgot to mention that I ran the memtest86+ the other day. It ran for 9 hours or so and did 16 passes with no errors.