For windows NTFS the limit was 4,294,967,295 files but dont know if this has changed since the last time I looked into it (days of win2k)
ext 2: The limit of sublevel-directories is about 32768. If the number of files in a directory exceeds 10000 to 15000 files, the user will normally be warned that operations can last for a long time. The theoretical limit on the number of files in a directory is 1.3 × 10(20). Thats 10 to the 20th power..... Imagine ext3 matches or exceeds this. NTFS information hasn't changed. Site to check is : http://en.wikipedia.org/wiki/Comparison_of_file_systems