When you install software, new, or again, it installs the original version of the ACR plug-in, maybe 6.0 in this case, and it probably just needs updated, via Help / Updates, and for CS5 you should get ACR 6.7.
If the camera the raw files are from is somehow newer on this computer than on the previous computer then perhaps you need to update PS, itself. Here is a list of what versions of ACR will work with what model cameras:
http://helpx.adobe.com/creative-suite/kb/camera-raw-plug-supported-cameras.html