The maximum filename length in Windows XP is 255 characters. Keep in mind that this number includes the pathname and the extension.
So, for example, if you have a file named 'stuff.txt' in the root directory, C:\, it would be nine characters long. However, if you moved that file into a subfolder named 'things', it would then have sixteen characters (don't forget the slash). The maximum filename length cannot be changed in Windows.