Windows 7 USB/external hard drive access denied (tried everything)

Seen this one over and over again. USB devices formatted on a Mac won't typically read directly from a Windows PC of any version!!
If you are trying to extract the data from those USB devices on a Windows PC, forget it, it won't work unless you take it to a professional who has special software to do this, and a whole lot of skill.

If you are simply trying to USE or REPURPOSE the 3 USB devices for storage on a Windows PC; I can help you with that. It's best to use a Linux-based disk utility to wipe or erase everything off of those 3 devices to do so. Many of us here like and use DBAN *Derik's Nuke 'n Boot*. It's available free on public domain--use Google to search for it. You can also get it on the excellent UBCD boot disc by Benjamin Burrows, also public domain, but pretty tricky to create. If you have a friend or a local Tech they may loan one to you or make you a copy for a small fee. DBAN will then write zeros in the low-level format of each of your drives [MAKE CERTAIN YOU HAVE ANY DATA BACKED UP OR REMOVED FROM THESE DRIVES AS THIS IS A ONE-WAY DESTRUCTIVE OPERATION!!!].

Once you've done that, you can connect each of the drives, one at a time to a Windows PC via the USB port. Boot Windows and choose the default format via Windows Explorer (or File Explorer if you have W10). Format the drive, and it should then be usable on your Windows PC for storage of files and folders. If you do get options for format type, the best to use for the 1 flash drive, is FAT32 which you mentioned you tried in your post. For the 2 USB hard drives, I suggest you use NTFS especially if they are 1TB or larger. If either of those drives is 3TB or larger, you'll also have to format it in GPT, not the default MBR format in W7. You can google how to do that or search our forum here for instructions on how to do that. If you do have a >3TB drive and you don't take the time to format it in GPT format, you may not be able to read it on a different Windows computer, especially if that computer has a modern UEFI BIOS in it's Motherboard.

This solves your problem if you are just trying to repurpose those 3 drives. If you are trying to recover data, that's much trickier and you'll have to take all 3 drives to an Apple Certified Tech and pay him to do what we call Data Recovery for you. Typically, it's $35-$125 US per device to do. If you don't have an Apple Tech near you, you can take to the local Apple Computer store in a Mall near you (that's where most of them are located), and take the drives into the Genius Bar inside of the store and tell them you want to do Data Recovery on those 3 drives. They will quote you a price and tell you to come back in a few weeks and they will have them recovered on DVD discs or another external HDD and all of these will be readable on any Mac.

The rub here is that Mac has a proprietary disk format, just as modern versions of Windows have (W8 and above especially) a proprietary format as well. If you need to be further convinced, simply take any USB external HDD or Flash Drive that's been working on a Windows PC, and try to plug it into one of your Macs or an iPad--it will not read it! In some cases, you'll see files or directories, but it you try to open something like a Word or Excel or PDF file or a photo or a .mpeg movie--no Bueno! This has been this way for decades, and won't change anytime soon.

Best of luck,
<<<BIGBEARJEDI>>>

The OP mentioned they'd formatted it through disk management and still got the access denied. So this isn't a mac format issue.

Never had any issue with the drives on other windows machines.
Moreover, the usb' key was never formatted on mac... only a Windows's use.
Btw, I even tried to format the USB key (which is my test device) to NTFS, still got the access denied, even with only one partition (like it is suggested by tuxera)