How many external drives can Windows PCs recognize at once?

Is there a limit on how many WD external hard drives can be connected to a PC at once using USB ports? I am on a single-user Win 7 OS (64-bit) system. I have five separate WD external hard drives. Each stores audio or video files. I work at home and I edit the file names for my customers, and eliminate duplicates, etc. so I really need to be able to see what is on all five drives. No matter what I do, only two drives will appear in the list of connected devices in Windows Explorer. It has nothing to do with the drive names because I can change the drive name and it won’t show up, but if I unplug a different drive, the one I changed WILL then appear. It sounds to me that there is a limit on how many devices the system will recognize. Is there such a limit? If yes, is there a way around it? I really need to see all the files on my external drives. I think this question relates to a lot of other people’s questions, but I can’t seem to find the answer to MY issue. Thank you.

I’m running Win 7 64-Bit Home Premium and have had 5 External WD drives (2x4TB, 2x3TB, 1X2TB) all powered on and recognized at the same time without a problem.

The only problem i had with adding more … was my powerboard had exceeded the maximum current draw (i think it’s a 10A Board) … and also your PC Power Supply Wattage is likely important too.

I guess, to summarize the answer to the question …

as long as you have enough power and ports … then as many as Windows Drive letter assignment will allow (From A~Z ie. 24)