First to say that it's time to change your VAR (Value Added Reseller)! Clearly they're not adding any value when you have a clear problem ... Who is it by the way; CADTEK, Solid Solutions or NTCADCAM? If it's not one of those you're dealing with the small-fry end of the UK VAR market unfortunately and I'd change now.
Anyway, to your problem. Solidworks is opening another instance of itself because presumably you're double-clicking on a file (part, assy, drawing) in Windows explorer while you already have Solidworks open. This will not just bring that file into SW as you might expect. There has been a fair amount of discussions about this last year and earlier this year (have a look at one discussion here). It's a Win7 thing and you need to play with the registry settings.
If you just drag the SW file you want to open into your SW window or use the File>Open dialogue you won't get the problem. Careful if you're in the assembly mode, as to open a new file by dragging, you need to drag it into SW outside the graphics area otherwise you'll insert it into your assembly.
yes thats a great idea - I won't be using them again if they cant spare a few mins of help! Im not one to name and shame, but feel a bit let down.. Their Solid Solutions.
Im thinking that it is a registy issue but being on a work computer they wont allow me to tinker with it.. over to the IT dept!
I guess if anything ill have to remember to always have not to have more than one open - learnt the hard way and lost half a days work :/
Thanks for your reply Keith!!
This might be worth trying: Right click on the SolidWorks file in windows explorer and select properties. Now check what program they have been set to open with. Even if they are set to open with SolidWorks, reselect SolidWorks from the list. Try opening SW file by double clicking on them while SW session is running.