Will reactivating a dynamic drive showing offline wipe the external drives content

[maxwell4]

Have two external hard drives but all of a sudden my pc will only read one at a time. The other when plugged in states offline - if I try to reactivate it with both plugged in will it wipe the contents of the one I'm trying to activate?

 

[ronintexas]

Are the hard drives powered by the USB port, or do they have power adapters?

Also - have you tried different USB plugs for the drives?

Have to tried scan disk on the drives when they are plugged in one at a time?