VT,
A TB is a Terrabyte or 1000 GB (Gigabytes), so a 1TB drive has slightly over three times the capacity of your laptop's 320 GB hard drive.
The 1TB Samsung on Amazon is a very good price, but BE CAREFUL. It requires a USB 3 port. Depending on the age of your computer, yours may only be USB 2.
So check the specs on your computer's USB ports, and make sure you choose the right version of USB, before buying a hard drive.
Having said that, get a 1TB drive and use it for your backups. I agree with FOR's comment about backed-up clones of C drives only being reloadable onto the 'father' machine.
My recommendation, given that there is a lot more space on a 1TB drive than you need to back-up your hard drive, would be to partition the 1TB disk into two logical drives - one of 350 GB (slightly more than your laptop's 320 GB) and one of the remainder of the drive. Then when you attach the drive, Windows will see two new drives. Use the smaller one for automatic, incremental back-ups and use the larger one, as FOR suggests, to make copies of all your important files (documents, videos, pictures, email folders, etc.) on a regular basis. Incidentally, because of the way formatting works, the total usable space will not add up to 1TB, it will be slightly less.
I'm not fully up to speed on Windows partitioning these days, but here's a good link from a safe source (I Googled "partitioning an external hard drive"):
How to partition a hard drive | PCWorld
I also looked up Acronis and it looks like a suitable backup program for your needs. Not free, but then look at the cost as an insurance premium.
Finally, I should mention that I've had four hard disk failures in my computer career, and in every case, there were tell-tale signs before the final failure, i.e. corrupted files, bad reads and writes, corrupt sectors, etc. So the moral is any time a disk displays symptoms like these, it is time to back it up and replace it.
