In my recent adventure of getting OpenCL working on my laptop (see: Catalyst Install Manager not installing device drivers) I was having a hard time figuring out why even though I had the latest drivers for my card (an ATI Mobility Radeon HD 5870) and even the AMD Accelerated Parallel Processing (APP) SDK (formerly ATI Stream), OpenCL was not working. My GPU was not showing up as an OpenGL device using GPU Caps Viewer, and the examples from the AMD APP SDK were clearly stating:"GPU not found. Falling back to CPU device."
After a bit of trouble and frustration I found a post by animal007uk in the thread http://www.techpowerup.com/forums/showthread.php?t=140419 (go straight to their post here)
For the Mobility Radeon card you need the specific Mobility drivers which are available (Win7 64-bit) at http://support.amd.com/us/gpudownload/windows/Pages/radeonmob_win7-64.aspx as mentioned in animal007uk's post.
Now OpenCL is working perfectly! Yay!