Windows 7 image - not sys prepped

Today I had a Windows 7 PC with a borfed HD. Putting a new HD in I then used Clonezilla to deploy an image stored from what I thought was this PC after it's last rebuild. Turned out I was wrong and it was actually from a similarly named client. The image went on fine and joined the network ok and I have since renamed the workstation. What problems am I likely to run into because the image was from another Windows 7 machine that had not been sysprepped?

Secondly would I be now better off building an image to hold on one of our 2008 R2 servers - if so using what?

The OS itself should be fine as log as you aren't running any software relying on the machine's SID being different (there was some shoddy security I read about that used the SID value as the encryption key). As long as you don't get any issues with services that may have registered with your servers, e.g. WSUS or anti-virus server, I doubt you'll see any issues.

You could look at FOG, WDS, MDT. Maybe even look at doing the OS deployments with VHD files so you can just back these up from the clients rather than use complete drive images.