Site definitions for windows server 2003

Hello all,
I've been struggling with the folloiwing for weeks... I'm trying to develop a system on a client's windows server 2003 based pc. however i've tried millions of times to define the site as usual but dreamweaver wont acknowledge my testing server once i exit the site definitions dialog box - whilst the local and remote checkboxes are ticked, the testing server box is greyed out. i've downloaded the SP1 update patch as recommended by Adobe but to no effect. It's drinving me nuts.

Any ideas?

Cheers
Toby