404 (Not Found) Error When clicking on MySite "My Profile" tab in SharePoint

This error is vexing, though there's a simple solution documented in MS kb924399. I've summarized the solution below with some assumptions about settings that folks normally use. In short, the problem is that there isn't a site collection set up using the appropriate template in the MySite web application. We'll correct that in a few steps. Note: it's entirely possible--even likely--that you've already got a site collection created at the root of the mysite web application. If this is a single personal site, that's part of your problem. This site will need to be backed up and deleted before you can go further, assuming that all of your other personal sites are using a different path. First, we need to create the managed path that SharePoint will use for this site collection.

This can be anything, but most people will have created their sites with the default root ( / ) site collection. So we'll go with that for our purposes.

To do this, click on Application Mangement -> Define Managed Paths. Make sure, once the defined managed paths screen comes up, that you've got the correct MySite web application selected in the top-right. Go ahead and create the managed path at the desired location.

Next, we'll want to create the site collection using the correct template.

Click on Application Management -> Create Site Collection to bring up the site collection screen. Make sure you've got the correct web application selected on the left, and then select the managed path you created in the step above for the URL.

Give the site collection a title, like 'Personal Sites', and -- here's the money part -- select the "My Site Host" template from the Enterprise template tab.

Fill in the site administrators fields appropriately and click on OK.

After doing these steps, the My Profile tab should work again.