XAMPP for any Windows is 32 bit but will run quite well on 64 bit Windows.
You should be logged in to W7 with full administrator rights for running XAMPP successfully.
Do not install to C:\Program Files (X86) or it will fail, instead use the default location of the root of a drive for example C:\ so you end up with C:\xampp and all will be well.
Another tip, do not select to install any component as a Windows service when using the buggy installer version as this often causes issues with some installations.
Yet another tip, download the zip or 7zip version then simply drag the included xampp folder to the C:\ drive then run the setup_xampp.bat file found in the xampp folder.
(Some say there is no need to run this file if installing to the C:\ drive but I find it sets the correct full paths throughout the installation regardless
Also use the newer Control Panel Version 3 which can be found in the xampp folder:
instead of the older 2.5 version.
You can then replace the included version with the very latest and greatest version by downloading from the post linked in my signature.
Drag all the files and folder contained in the CPv3 folder into the C:\xampp folder and overwrite when asked - do not extract the CPv3 folder extract only the contents of the folder.
Any issues please feel free to post a topic in this forum if it can't be found by doing a forum search.
Good luck and enjoy XAMPP.