OK, i found a fix.

it was all down to the assemblies that were included. and SQL Server express.

I had SQL Express 2008 installed and this worked fine on the XP laptops. however.......

Initially, there was a message saying that 2008 had 'known compatibility issues' with Wondows 7. But i plowed on through and everything seemed to be ok.

I tracked the error to a dll that 2008 seems to remove.

I uninstalled 2008, located a copy of 2005 Express and voila....all was well with the world.

so, there is your answer. if you are using windows 7, and you want a SQL Server database, use 2005.



thanks again for the help.