External hard drives question

Hi everyone, I am new to this forum.

I have a WD My Book 500GB external hard drive. I can use it on both my mac side and my windows side, but it keeps giving me an annoying message saying that I didn't properly eject the external hard drive on the mac side (but I *did* use the eject buttom!).

What happened was, I had the My Book drive connected to my old PC and it worked fine. When I bought my iMac in Oct, I connected the same drive to my iMac and it still worked fine. The drive is/was formatted as MS-DOS (FAT32)).

When I installed Parallels, I realized that I couldn't see the external drive when I was in Windows. So I ejected the drive while on the iMac side, went to Windows Parallels, plugged in the drive, and it showed up on Windows. The problem is solved (I can read/write to drive from both Mac and Windows), however, I keep getting an error message saying that the drive was not properly ejected from the iMac and that all the data is lost.

I've been ignoring the message but it's a bit scary. Does anybody have any ideas on how to stop it?
Thanks!
Fio999

 

Probably some files are open on Mac OS side from that drive?
Use lsof |grep DISK-NAME
to check