Bought this to connect to my VW MK IV Golf (2001) 130 PDTDI and I can confirm it works.
Had a panic though - if you only connect the cable to the laptop / PC without connecting to the actual car then it will report that the COM port is OK, but the interface is missing... DUH - I connected it to the car, turned on the ignition and hey presto - worked.
Unfortunate thing for me now though is I found a fault on the car that I wasn't expecting. Reset the fault codes and it's never returned - I suspect I disconnected the ABS sensor when the battery was still connected (which will result in an intermittent fault code) - Well impressed.
Didn't use the software on the supplied CD as have a more up to date version from elsewhere.
Will recommend this to any VW Golf MK IV owners. With the right software there's a lot of things this cable gives access to.
** Forgot to mention - Version 409 of VagCom confirmed working on my Windows 7 laptop. You can go to RossTech web site and download "lite" versions but you need to register the software for full functionality - however just google Vagcom for more information on vagcom software