Mapped drive prompting for application to open with

Hi
I'm hoping this is the right section to ask this question in as it relates
to a network drive problem.
I have a windows xp 64bit edition PC which has just had the Sality virus
cleaned off it.
It's all perfect now except for one little problem which is that when you go
to "my computer" and try to open a particular drive mapping the pop up window
appears prompting to choose what application you would like to open it with.
If I select iexplore it opens fine but the tick box to say always use this
program is greyed out even when I'm logged in as administrator.
All other drive mappings work ok it just this particular one and it still
occurs even if I change the drive letter it is mapped to so it seems to be
associated with the unc path not the mapping letter.
I tried an application called fixit that i got a link to on the experts
exchange website but it doesn't work as it says I need xp or vista to run it,
I'm assuming this is because it doesn't work with 64bit edition.
Any help you can provide would be great
thanks in advance