If you have a Windows7 workstation you can reciprocate the error yourself, by simply taking the following steps:- (Nb; your browser must be Internet Explorer v6 or better, Mozilla Firefox 1.0 or better, or Netscape v7 or better... and you must have Adobe [Acrobat] Reader installed on your system).
1) Visit... http://www.parcelforce.com/portal/pw
2) Click 'Send your Parcel now'
3) Choose 'Pay by Credit Card'
and tick to accept T&C's, then press 'Continue'
4) You may have to wait a while whilst the next page loads... but when it does, you'll be told Windows7 ain't supported...