Further to my last, I have solved my issue and this might help others. The only difference bewteen my laptop where everything worked and the desktop where the upload failed was the desktop had a newer version of Arduino.exe. So I looked around the settings a bit and sure enough the new software defaults to teh bard with the ATmega 328 chipset whilst mine has the ATmega 168. Once I changed this setting all was well.
The setting is under Tools>Board ;D