OS is your operating system...Windows 98, XP, Vista etc.

You don't have to pay for the Beta. All you have to do is click on the 'get basic' button, answer the question about copyright infringement & then when you get to the download page, click on the 'get beta' button.

In post #2 I posted links with instructions for deleting the preferences folder & you said that the tips didn't work...so I thought you would've tried them.
Just go through the instructions slowly & see how you go.