have just installed Clam on a BartPE Startup disk and randomly tested it on a laptop I've only just set up.

Well impressed. But also worried. It claims to have found - in the pagefile.sys no less - a virus with the name vgen.1055.0 which I've never heard of and nor has anyone else on the web - including the major antivirus vendors none of whom have it in their online libraries. There are half a dozen sites listing it amongst a list of worms, but nothing explaining or justifying that inclusion. No commentary is available anywhere. (at least not that I could find)

So does anyone here have any clue what it may be?

Was this by any chance a PUA detection? If you have ClamWin's PUA detection turned on, the PUA signatures trigger on hacker tools, which are not necessarily viruses/malware, but they can be used for that purpose. If not a PUA, then I suggest that you upload the file containing the "malware" to Jotti and see what over 20 other scanners say about it. If any of them spot something, they will have a name you can cross reference. If no other scanners spot it, then tell Clam it is a false positive at https://cgi.clamav.net/sendvirus.cgi on the Web.

Regards,

do not scan pagefile, remove it if you want, clamav may found a pattern signature that belongs to the one that loaded in memory when windows was running
you may found random viruses just because the pattern was loaded by a running av