How do I test and determine...

well, you know what you've got. So if you've got a speedy disk and the tests are low on disks, then there is something wrong in that department. And so on. 

taskmanager, tab Performance, has a Resourcemanager button that shows you far more details on what the machine is doing.

VM by default is 150% of your RAM, no sense in going down from 25G to 16G

Notorious slow-downers are virus scanners and malware checkers, especially if more of them are running in parallel. I see IOBit malware remover, AVG, and perhaps even more (and I kicked out Norton and then AVG for wrecking performance, but that might be history). Use one for all protection, I'm running MS Security Essentials, it's good on performance.

Another trick is to start Windows in Safe-mode, it won't load most drivers and background processes. When that gives you the speedy machine, it's in that area. When it stays slow, it's the machine. XP is not the way.

Wish you luck :-)

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Usually I'm wrong. But to be effective and efficient, I don't need to be correct or accurate.

visit www.aRtBeeWeb.nl (works) or Missing Manuals (tutorials & reviews) - both need an update though