Manifest may not be valid or the file could not be opened.

Question

I know it is a very commonly faced problem. But, there is a slight difference, my WPF installs perfectly and runs on Windows 7 and Windows 8 OSes. But, when tried to install

Answer 1

I have seen a similar issue before where a particular WIndows OS could not 'understand' or validate the results of a certificate hash due to missing crypto providers, in my particular case it was related to using a X509 certificate generated using a v3 template for the clickonce signing.

SignatureDescription could not be created for the signature algorithm supplied

The highlighted part of the message combined with the successful installation on several machines before failing on the WinXP machine would indicate that you are also running into a similar problem - WinXP doesn't know about the crypto algorithmn specified in the certificate that you've used to sign the clickonce.

I don't know of a good solution to this, normal advice you will find on the internet is to use a v2 template to generate the X509 instead of a v3 template, but this is not necessarily a good solution and is beyond the capabilities of most organisations (espcecially as most people use a bought certificate rather than certs generated from their own Certificate Authority).