Not sure from which version, but mIRC refuses to run if it's named something other than mirc.exe, probably because there are a lot of trojans out there trying to use a hidden mirc instance with a script.
Personally, I wouldn't bother trying to use that Tablet thingy and try to put something usable on that laptop instead, if it is at all possible.
Anyways it sounds like simple path based software restriction rules, which can be edited in Control Panel -> Administrative Tools -> Local Security Policy, under Software Restriction Policies on a regular Windows XP.
In case you don't have such, you could also try looking into the registry, for me these restrictions are stored under:
Just make sure you don't change anything you do not understand and don't know how you could restore later.