Recently, Vista started opening folders in a new window even though “Open each folder in the same window” was selected in the folder options. Obviously something had changed but I didn’t know what. There were more indications that something was wrong, including:

• Explorer opens folders in a new window, ignoring the folder options setting.
• The Windows flag on C: is gone.
• DVD-drives are labelled as CD-drive.
• Trying to access a CD/DVD results in a Format blank disc dialog box.

Searching the internet resulted in heaps of complaints about the new window issue so finding the right fix wasn’t easy. It turned out that Internet Explorer 8 was the culprit. So there you have solution #1: uninstall IE8. Actually, that’s not a solution so I wasn’t satisfied

Another solution that I encountered a couple of times suggested to launch IE8 as administrator. Several users reported that this method fixed the problem, but it certainly didn’t fix it for me.

Eventually, I found a comment on the IEBlog with a list of 19(!) steps to fix it. Fortunately, and as noted in the comment too, step #11 seems to be the critical one. I was able to solve all issues mentioned above by doing this:

1. Open a command prompt as administrator (right click -> Run as Administrator)
2. Type: regsvr32 actxprxy.dll
3. Click OK in the popup window.
4. Reboot

And Vista was back to its normal self. YMMV!