BSOD on startup - affects several PCs

Our school has a mix of about 100 XP and W7 PCs in a 2 x Windows Server 2008 R2 domain. A couple of weeks ago, three W7 machines crashed on startup with a BSOD. A superficial look at the crash dumps show they are similar. The network is a 1GB switch acting as backbone, with a number of 100MB switches wired with Cat5e cable to it; (but 2 locations connect via fibre). Also, (and this may be crucial), we have expanded a few ports with cheapo Genius 5-port switches where there is insufficient capacity. The first sign of trouble was when I connected 4 new laptops via such a temporary switch whilst I was configuring them. Two of them crashed whilst downloading windows updates from our WSUS. When I moved the PCs to a port on a permanent switch, they didn't crash again. I thought TCP/IP was designed to survive nuclear attacks, so perhaps this is a red herring! As far as I can see, during normal user activity there is no trouble.

I will post the crash dumps when I next go on site, but I've posted this in advance in case it strikes a chord somewhere.

The reason I haven't gone to M$ is that we are a small state school without much money to spend on support, so I should be grateful for your assistance.

Hello Ken and welcome to Seven Forums.

You may be correct in thinking the problem rests with the "cheapo Genius 5-port switches". :)
But without the crash dumps it's going to be difficult to say for sure. Please follow the BSOD posting instructions here:

Blue Screen of Death (BSOD) Posting Instructions

Will do - but whenever I visit the school, the teachers have taken the offending laptops home! And we currently have a bigger problem to fix.

Unfortunately, the SF diagnostic tool crashed, so I can't send the required data. I have got windbg installed, so can I just send you something from that? I see that the .DMP file is too big to send even when zipped.

I have uploaded the error repot from the diagnostic tool.

I did the next batch of laptops connected with a better quality switch and the problem did not recur.
I think it best if we abandon this thread as the problem is not repeatable.

Thanks anyway.