Seems as if CPU-Z is reading two 1000mh cores. I thought the core duo was two 2.0gh cores? Is this an error on the software or is this a dual core 1gh machine?
It's throttled down, if your CPUs aren't doing much, XP will slow them down to give you more battery life. It's perfectly normal. As soon as you need them, XP will speed them back up.
Stays at 1000.0MHz, 1001.0MHz, 999.0Mhz, 2000.1MHz, back down to 1000-999. I did see 2000 tho when I loaded adobe ps on windows. I'm guessing what ewinemiller said is true as it only shows clock speeds of 2000 when its being used. It should not jump to 1900, 1700, ect.. like you have said, it should only stick to 1000 and 2000 when in use.