What's the best plan of action?
Ok all the important stuff is backed up to an external HD and also the most important stuff (photos & music) is also on an internal 200 gig HD so I'm not terribly worried but I can't be arsed installign all my software all over again and Windows for that matter...
Can I clone my C drive to another hard drive and swap them over?
Yes
I use Macruim backup, http://www.macrium.com/
It's free and seems to work. I've used it for real once when my media centre PC started to play up. Cloned it over the network to a shared drive, installed a new drive then pulled it back, after booting from a USB stick.
There's various cloning solutions. I use Acronis - well worth the asking price.
One tip though, if you're going to do it, do it -before- the drive fails completely. The longer you leave it, the harder it's going to be.