Understanding CPU usage

[Diggs]

I have a Xeoma installation that runs on a HP t5730 thin client (Semperon 2100+ w/1 GB memory) for the last 1-2 years. It has 4 jpeg WiFi cameras and it records to an external HDD. It used to use 3-5% CPU running under WinXPe (Windows XP embedded) with both client and server together minimized. Viewing the client or playing recorded clips would bring the CPU to 100% but the low CPU usage in minimized window always surprised and impressed me as I am always reading about the high CPU usage others were experiencing.

So this week the thin client becomes a thick client with 2 GB of memory and a 64 GB internal SSD HDD along with Windows 7 Pro (32-bit). This thick client used to idle at 0-3% CPU. Now the exact same install of Xeoma and its 4 cameras and this computer now idles at 35-40% CPU showing the load is all from Xeoma. Can someone tell me why the extreme CPU usage change between the two different 32-bit Windows versions? Obviously WinXPe is more efficient, but Win7 requires 10 times the processor power for running Xeoma? Doesn't sound right.

Can anyone shed some light on what I'm seeing?