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This question has been asked several times before in the time that I have been a member. If you have not resolved it yet, I can't remember the subject of threads, but if you search through the 'Installation' forum and the 'Q and A' forum you should find the answer to this.
If I recall it will probably be a permissions setting. Once you go past the first page XOOPS will be trying to do something, like write a cookie or obtain some information, but the lack of permission will be blocking it. Check that the IUSR_MACHINENAME and IIS_WPG users has access to your web folder.
Honestly - do a good search and you'll find the answer.