Clean install of Mavericks via Snow Leopard using Time machine dat recovery When purchased, my iMac came with Snow Leopard, plus installation disks, but I recently upgraded the OS to Mavericks, in order to use the latest iteration of Garageband, i.e. Garageband 10.1. 

Garageband 10.1 does not run at all well, but I don't know whether it is a glitchy, buggy program, or a system wide issue on my machine causing the problem. It occurred to me I might back up the system I currently run using Time Machine to preserve data, perform a clean install, using my Snow Leopard disks, then upgrade via the App store back to Mavericks, (because Garageband 10.1 cannot run on Snow Leopard), which would effectively give me clean Mavericks installation. I would then reinstall my data from my Time Machine Back up.

Is this a sensible approach which might work? I'd appreciate any advice. Many thanks, George Bolam.
First thing is to backup your system but you don't need to reinstall your computer via DVD. Instead there is a terminal script which will take the version of the Mavericks installer you got from the Mac App Store and install it on a USB stick. Pretty sweet stuff: http://support.apple.com/kb/HT5856

You need a USB stick roughly 8 GB or larger and it should be erase before hand. There is another version of the command line that is as follows


  sudo "/Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia" --volume /Volumes/Untitled --applicationpath "/Applications/Install OS X Mavericks.app"


With this the USB drive needs to be called Untitled and this will do all the necessary steps in the background. Be aware it will take 30-40 minutes for this to copy over but when it is done you'll see a $ sign.

Now with that created please restart your mac, hold down alt and choose your USB device. Once you have the install option erase your hard drive through Disk Utility and then you can proceed with a fresh install of Mavericks.

I would recommend re-downloading Garageband from the Mac App Store fresh instead of transferring it from TimeMachine... hope this helps you out and if you have further questions just comment.