Looking through the services and security options on the offending PC, I could not find anything wrong with the Windows settings.
However, I CAN access particular drives on the PC by using \\ITCNVRT3\L in the 'Run' command. So, to simplifiy this, I made shortcuts to all shared drives in the Shared Documents folder, then run \\ITCNVRT3\Documents, and from there have access to all drives and shared folders that have shortcuts in the Documents folder. This works fine from the other XP computer, but from Vista machines there are a few problems. Some of the drives are accessed no problem, others are not accessible or think they are DVD drives, although if I try to access them with their actual share names (e.g. \\itcnvrt3\Storage2 (P) ) this works.
A pain in that it is not simply a double click, but at least it IS allowing access.
I can only think there is some corruption in the security policies.
I am quite satisfied that it has nothing to do with Blink Personal.
Before anyone suggests it could be to do with previous AV suites imperfectly uninstalled, I ran a force uninstall programme and DID get some F-Secure and Netgate registry files deleted, but this had no effect on my problem, however it could be that the uninstallation of these programmes played some part in corrupting some files and/or registry entries
So, my conclusion must be that due to some corruption in the security policies, I will just have to suffer this until I can do a full destructive recovery.
The other XP computer was a fresh install and Blink was installed immediately after finishing the Windows install (It had been on Vista 64 bit, but I was getting fed up with problems on this version. I still have one on 64 bit for testing, but prefer Vista 32 bit and XP 32 bit for ease of use. - Nothing wrong with Vista 32 bit, it just needs a powerful computer, - 64 bit would be better if more software and hardware companies would supply 64 bit versions of software and drivers.
Thanks also to Blue, but I used to be a network administrator (albeit it with NT4 then 2K) and am at present working part time as a repair tech, and have experience in XP, Vista, and Windows 7, (not to mention fond memories of 2K, and not so fond memories of NT4 and 3.1 !) so these suggestions were already covered ! Blink is installed on all the machines that could not access the offending computer. I bought 6 licences, and will probably buy one for my laptop. I will wait for the final release of Blink for Windows 7, but am quite happy with the Kaspersky beta for the moment - may consider the Win 7 beta, though..... - we'll see.
The simplest answer of all for easy and secure networking would be to upgrade all to Windows 7, but that would require a large financial outlay !
I did install and run SubInACL and run a .bat file to clean up some permissions, but this hasn't had any effect on the problem.
When I can face the job of backing up application data, etc. (Thank the lord for File and Settings Transfer Wizard and mozbackup ! - AZ/Vuze is simply a matter of copying programme folder and applicaion data folders and pasting and overwriting) and doing a re-install, I will post back here if it has been successful, and with any comments that may be helpful to others coming up against this problem.