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#11
A CPU can only run one thread at a time, and each thread gets a quantum on the CPU (an amount of time it's allowed to run before the scheduler checks to see if it needs to be pre-empted by another thread waiting, or whether it can continue running). Logicearth is correct, there's no single-CPU cap on percentage, and you need to be very careful when looking at *total* CPU usage (like that reported by resource monitor or task manager), which shows you a percentage of total CPU time across all CPUs, versus actual CPU usage per CPU as you would see in something like perfmon.
What you saw was accurate (and yet inaccurate) in that you were using 25-30% of total CPU time, but across 4 CPUs - 100% across 4 CPUs means that when you see a 25% number, you're very likely looking at 100% on one core (100% of 1 core "averaged" out as total CPU when there are 4 CPUs shows up as, you guessed it, 25% approximately).
Windows 7 does not spread a single thread out amongst multiple CPUs - when the thread runs, it can run on one CPU only. What you saw was accurate - a single CPU thread will consume a single CPU (up to 100%) during it's quantum, but task manager and resource monitor (by default) show you the averaged CPU usage number across all the available CPU cores - 100% used on one CPU will show up as (approximately) 25% CPU usage. If you want detailed information, you need to change the options in task manager or resource monitor to show detailed CPU usage across all CPUs, or use performance monitor to view CPU usage.