I have oneTouch4 external hard drive and is OK until now. But all of sudden it shows access denied. And in properties it shows 0 bytes. But is accessifor scanning. I don't know how it is open to explore. All imp personal data and my system backup is located in that.
Can any one help how to access it. I am using vista ultimate.

Try looking at this and see if it helps...

Seagate Knowledge Base (http://seagate.custkb.com/seagate/crm/selfservice/search.jsp?DocId=203795)

See if drive is recognized in properties for the drive.

Right click on the drive in windows explorer and click properties.

What is listed there for used space/free space and
File System