no unfortunately you cant reinstall it once you have used up your trial period. i think when you download the program, something else is also downloaded that tells the computer that you have used up the program. So after that, no matter what you do, everytime you reinstall it, it will tell you that you have already used up the program.
You can either try and download another version (which is hard to do because it is hard to find another version and you can only find it on other sites, which gives you no guarantee that there wont be a virus), or you can just go and buy the program, if you are really interested in web design.
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