The install process should have added "Fractal Theme" and (from v3.0) "Spirofractal Screen Saver" to the list of programs that appears in Add/Remove Programs inside Control Panel. You can use these options to uninstall Spirofractal Desktop theme. Uninstalling "Fractal Theme" does not uninstall the screen saver, so if you want to you can keep the screen saver and not the theme.
Before removing the theme or screen saver select another theme/screen saver using the Desktop Themes part of Control Panel, as otherwise it is possible not all files will be deleted. If you did not use the Install program to install the theme, then this may fail. In this case you can probably get the uninstall to work by re-extracting the files in the zip download file to the same place you installed them from in the first place and retrying the uninstall.
If necessary, you can uninstall manually by deleting the c:\Program Files\plus!\themes\fractal and c:\Program Files\Spirofractal directores and deleting the two screen saver files listed below from the Windows System directory (usually c:\windows\system). This directory may have another name such as c:\win95\system if you have a non standard installation. On Windows NT it is called c:\windows\system32 or c:\winnt\system32.
Please be very careful when deleting files from the system directory. If you delete the wrong files you may stop your computer working. Make sure you send files to the Recycle bin first before permanently deleting them, so that you can recover if you make a mistake. If you are not confident you can do this correctly I advise you just to leave the files on the machine. They are quite small - most of the space used by the theme is taken by the sounds and wallpaper and not the screen saver. They will not affect operation of your computer in any way.
If you are using version 3.0, simply select "Spirofractal" in the Add/Remove Programs Control Panel screen. For version 2.x there is an uninstall batch file in the directory where Spirofractal is installed, which should work OK. This should be in your start menu as well. Spirofractal v2 is not in the list of programs that can be uninstalled in Control Panel.
You can uninstall manually by deleting the c:\Program files\Spirofractal directory using Windows Explorer, and the screen saver files, which are the same as for the Desktop Theme version. You can use display properties in control panel to select another screen saver. There are a few registry entries for version 3 of Spirofractal. These are in HKEY_LOCAL_MACHINE\Software\Alun Williams and HKEY_CURRENT_USER\Software\Alun Williams.
Manual uninstall won't remove items from the start menu. In some cases automatic uninstall of version 2.x may also leave menu entries as well. If you are using Windows 98 or installed the desktop update with Windows 95 or NT when you installed Internet Explorer you can remove items from your start menu by right clicking on them and selecting Delete. If not then you have to right click on Start, and select Explore. Then you can navigate through the folders until you find Spirofractal entries. These can be deleted.
Another way to find all the folders you need to delete is to use Find Files or Folders. Search for *fractal* on My Computer. Check inside any folders this finds. If there are Spirofractal entries then delete the folder. If you have installed other fractal programs then it may be best to use the advanced tab to limit the search to folders.