Over 1 year ago, I created a self-signed certificate in IIS 7.5 and exported it. I then installed it for IE9 (it may have been IE8 at the time), which worked fine until a year later when the certificate expired. I have put this off, but today I created a new self-signed certificate in IIS, exported it, and attempted to install it in IE9. The problem is that for whatever reason, IE cannot seem to forget about the old, expired certificate. Here's what I tried initially: Accessed my ASP.NET application and see the Certificate error. Clicked "View certificates". Clicked "Install Certificate" and then Next/Next/Finish. At this point, it says the import is successful, but it still only shows the expired certificate. I've tried simply double-clicking on the exported certificate on my desktop. Initially I chose to automatically select the certificate store, but then I tried it again and manually selected "Trusted Root Certification Authorities". I've also tried dragging/dropping the certificate over an IE window and clicking "Open". The process is then exactly the same as it is if I had double-clicked on the certificate, but I had hoped that this would somehow specifically tell IE to use this certificate. I tried opening MMC and with the Certificate snap-in, confirmed that the new certificate was added under "Trusted Root Certification Authorities". It was also under my "Personal" certificates (I guess this is where it goes by default). Nothing worked, so I went through every folder in MMC and deleted the expired certificate. I also deleted the expired certificate in IIS. Nothing has worked. Any ideas? I see no clear resolution and I can't seem to find any posts related to this issue.