If 64bit systems could only run 64bit software you'd not have much more than the OS.
As far as I see there is no 64bit version of XAMPP downloads and you don't need one.
When you install change install location to C:\XAMPP for example or any other directory outside of program files, as system folders are only writable for setup via elevated priviliges during installs.
Also don't change any of the defaults. If asked whether to install Apache as service, don't, that also adds to the problem of htdocs access, as already said. By default two normal apache processes running with your own user account will be started by the xampp control panel, one for http, one for https.
If it still doesn't work, maybe something else on your system is already making use of port 80, eg IIS.
Bye, Olaf.