Firefox: 'Automatically Download'

I was downloading Custom Content for the Sims, and since they're all .RAR files, I set the notification that comes up, to open in WinRAR and then clicked the automatically do this from now on box 'cos I was downloading quite a few. Is there a way to undo this since now all my .RAR files are being saved in the Temp folders and are opening in WinRAR. I've looked on google, and it only describes how to click the 'automatically do this from now box' and not how to undo this. Can anyone help? (Happy Saint Patrick's Day)

Right click the file again. choose "open with" then uncheck the box.

Right click the download? Or the link?
And I think it only happens on Welcome to Mod The Sims,

the download

It says 'Open, Open Containing Folder, Go to download page, Copy download link.' If it's just to do with MTS, should I delete cookies?

Ok, open containing folder. Then once inside that folder, you should see the "sims" downloads you just did. Right click one of those files and choose "open with". Then you'll see the application it's currently opening with. Uncheck the box and you should be good to go.

I unchecked the box, but Firefox still opens RAR files from ModTheSims in WinRAR and saving the RARs in my Temp folder.

screen shot please, that doesn't really make too much sense after having you uncheck the box.

Can you screen shot your "temp" folder?

Or can you change your download location to either your desktop or another folder?

gladson I already tried that but to no avail,
Brady thanks for all your help, all the help pages I was on were talking about firefox 2.0-3.5, (Your advice would have worked for prev. firefoxes), It's here: Unable to download or save files
The fix was in the Help>Troubleshooting>Application Basics>Open Folder>Rename mimeTypes.rdf