CAD Files Open in New CAD Session

This is a new problem, it was fine up till last week...when I double click a file to open it, it opens in a new cad session instead of the window I already have open. I've looked up other threads but those solutions didn't work...I have both SDI and Taskbar set to 0.

Thanks in advance

I'm positive we've covered this before. I believe you actually have to edit the File Types under Folder Options in Windows Explorer. Highlight the DWG extension then click on the Advanced button. Under Actions highlight Open then click on the Edit button. Application used to perform action should have "%1" appended to it and the box for Use DDE should be checked off. That's how it appears on my system. When done just back out the way you came making sure to click on the OK buttons as you do.

I followed your instructions up to File Types and clicking .DWG, but i didn't have the Advanced button, i hit Reset and it works fine now. Strange though, I hadn't messed with any of that....

Thanks for the help!