@gtc no fair Combofix was deleting the ones that I was going to
Combofix is an exceptionally good tool, however, because of that it does get targeted by malware and can sometimes mess the system. But, there are safety tools built in which allow us to recover the situation. Obviously they are not publicised otherwise that would negate the effect
sUBs has a paypal link for donations at BC http://www.bleepingcomputer.com/combofix/how-to-use-combofix
How is your computer running now ?
Thanks to ComboFix, and your advice, my PC is running like normal again. For the first time on days I'm able to get some work done. As I said earlier I was slowly going mad trying to get explorer and winlogon replaced.
I'll now visit bleepingcomputer and pay my dues.
I realise that running multiple AV tools simultaneously is not recommended but at the moment for me it's a case of "once bitten twice shy", so I'll run both Avast and McAfee for the time being as they don't seem to be fighting each other and my system response is fine. Ironically I had just renewed my annual subscription to McAfee before I was bitten by the trojan and the new version I just downloaded contains quite a bit more functionality. However, in my direct experience McAfee's Virus Removal Team (based in Bangalore, India from what I gathered over the phone) were out of their depth with this particular trojan.
Thank you to all who have offered information and advice. You guys are like Red Cross medics to the battle wounded.