A signature collision issue can be easily solved.
Sometime you only need to right click and select online for that drive.
Other times is required to assign a different drive letter since the second drive is trying to use a letter that has been taken already by another unit.
There are multiple threads on the community that talk about the same Windows issue.
http://community.wd.com/t5/External-Drives-for-PC/how-to-fix-signature-collsion/m-p/46964#M2343
