This was a registry entry for Condor which was left over from an earlier installation. I deleted this through regedit, ran the installation, with Sophos on, authorised the services, including a registry change, and it all appears to work again. Just for info.
I have been having issues with installing the new 7.2.3 version; well in fact there have been a few problems with updating to newer versions on my own XP pc. It appears that Sophos really does not like certain files, and after installation, most of the executables in condor/bin folder would just disappear. In fact this has just happened again, leaving two files – condor_c-gahp.exe wghich I have authorised in Sophos as not being suspicious. Allegedly is suffers from Sus/Behav-115 error as being a suspect file. Each time I allow a file as authorised, so my only way around this is to turn off Sophos for a moment.
As soon as I restart the Sophos virus checker, it puts nearly all the condor executables into the naughty bin. This is not a general issue around our Labs builds.