class function NewCacheFile(const APrefix: string; AUserCache: Boolean = false): string;

aPrefix: 3 letter extension that identifies the file type. All cache files are treated as temp files by Windows and must have a .tmp extension so the prefix is used to preserve the mime type. htm, png, jpg, etc.

aUserCache: Create in the user cache (true), or global cache (false)

Returns the name of a new cache file.