In the Phorum settings, there is an entry called "Cache Directory". On Windows systems, the installer will have set that to the default location C:\Windows\Temp. The cache directory is used for storing cached data and compiled templates. You can change the location of your cache directory if you do not want the Phorum files to be in C:\Windows\Temp or if you see the following kind of error message:

Warning:
fopen(c:\windows\temp\tpl-default-header-a72fb9dd20915e5953aa9b07d3eb3871.php):
failed to open stream: permission denied in
c:\path\to\phorum\include\templates.php on line 184

In that case, you will have to change the cache directory setting to point to a valid location. We advise you to change it to ./cache (this directory is already in the Phorum directory). Make sure that the webserver can write files to this directory.