I/O error could mean a lot of different things wrong with the drive, bad sectors or the drive isnt reading right. I did have a drive that did that on a customers and noticed it was hot. So I put ice in two zip lock bags and then put the drive in a small towel and then put the drive between both bags of ice. It kept the drive cool enough to where I was able to get 90% of the files off of it. Where when it got hot it totally stopped working and didnt even report as plugged in.
So that is normally something I try with drives that are dieing hard, sometimes it does help because things stay cold lets it work better. So that would be worth a shot IF you can get the data.
If it is reporting as raw that means the file system on the drive is messed up as well, you can try format recovery or partition recovery software, but if the drive is on its last leg a scan from one of those might finish it off as those programs have to scan every sector on the drive to grab any data that might be on them.
I say ice the sucker and see if it helps at all.
Shane