I recently purchased a "code signing" certificate from Comodo . Comodo charge about half as much as Thawte who are about half of Verisign.
The certificate transfer process is pretty tricky and the certificate ends up installed in the Certificate store of the browser used to request and transfer it.
YOU MUST USE THE SAME BROWSER TO ORDER AND DOWNLOAD THE CERTIFICATE.
I recommend using Opera 9.6 to order and download certificates.
Because I had difficulties with the ordering and download process Comodo issued a replacement certificate. Unfortunately I then used the first certificate for code signing. Comodo had revoked this certificate and the ClickOnce install dialog indicated "Unknown Publish". However, there was NO indication in the Windows Certificate Manager "CertMrg.msc" that the certifcate had been revoked. This issue was only resolved when Comodo support told me the serial number of working certificate.
To install the certificate in Vista proceed as follows:
First export the certificate from the browser ( In this case Opera 9.63 ).
Tools->Preferences->Advanced Tab.
You should see a "Manage Certificates" button.
Press the button.
The browser certificate manager will be displayed. The downloaded code signing certificates should be shown under the "Personal" tab.
Select the certificate and press the "Export" button on the right side of the form.
A file create dialog is displayed. Give the exported certificate a file name and select to save as type "PKCS #12 (*.p12) This type is equivalent to the Windows .pfx type.
Follow the dialogs to export the certificate.
Now install the certificate into the Vista certificate store.First run the Vista Certificate manage program "certmgr.msc"
Select the Personal/Certificates folder and then Ations->All Tasks->Import
Select the file exported above ( be sure to filter on file type .p12 ).
Follow the import wizard. Be sure NOT to select the
"Enable strong private key protecion" VS Code signing cannot handle the password request
Place the certicate in the "Personal" folder.
The certificate should now be availabe for code signing in VS.
Good luck. Andy