Answer:

A component used by Win2PDF appears to be missing from your PC. Please follow these instructions to install the shared "Microsoft XPS Document Writer" component:

To reinstall the Microsoft XPS Document Writer on Windows XP, download and install the free "XPS Essentials Pack" from the following page:

http://www.microsoft.com/downloads/details.aspx?FamilyId=B8DCFFDD-E3A5-44CC-8021-7649FD37FFEE&displaylang=en

To reinstall the Microsoft XPS Document Writer on Windows 7, first delete the "XPS Document Writer" icon from the "Printers and Faxes" section of the "Devices and Printers" folder. Next, choose "Add a printer", and select the following options:
"Add a local printer"
"Use an existing port" -> "XPSPort"
Manufacturer: "Microsoft", Printers: "Microsoft XPS Document Writer"
"Replace the current driver"
Printer name: "Microsoft XPS Document Writer"

To reinstall the Microsoft XPS Document Writer on Server 2008, execute the following command:
dism /online /enable-feature /featurename:Printing-XPSServices-Features

After reinsalling the "Microsoft XPS Document Writer", re-run the Win2PDF setup program. Let me know if this doesn't resolve the problem.