1) I assume the drive itself works fine? You can see it in My Computer and add and delete files as you like...
2) I assume it's an NTFS drive? Sometimes they're formatted as default to FAT32, which isn't really what you want (your internal drive is probably NTFS). I think it'll tell you this if you right-click the drive's icon in my computer and click properties. If not, you can go into control panel, then to the administrator folder, then into the computer management program (more information here
http://www.ehow.com/how_6026_format-hard-drive .html )
Personally I've never used Acronis, I used to use Norton Ghost instead. It did the job, but wasn't that great.