From Aptana

It is really unacceptable for Aptana to be installed as the IE view-source default. And then require that 'regedit' be used to fix your bug. Next time I may just uninstall the product. Thankfully, I could revert back. Aptana is a resource hog for view-source. When I want to use Aptana to EDIT, I'll do that explicitly, thank you.

I agree completely. I just spent 20 minutes figuring out that Aptana made this change, which was very rude, imho. This is the exact key I had to change to return to notepad as source viewer:

System Key: [HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Internet Explorer\View Source Editor\Editor Name] Value Name: (Default) Data Type: REG_SZ (String Value) Value Data: Path and Filename of Editor (e.g. c:\windows\notepad.exe)