I have a friend who's looking to upgrade, so I had him run CPU-Z and got the following info from him:
 
Motherboard: Intel DG965SS (965G Express Chipset)
Processor: Intel Core 2 Duo E6300 1.86 Mhz (Conroe)
Memory: Kingston 1 GB DDR2 PC2-5300 (512 x 2)
Video Card: Geforce 6600 LE
 
Some other settings...
 
CPU Multiplier: 6
Bus speed: 266
Which gives a core speed of 1.6 Ghz (why isn't this 1.86 Mhz?)
 
Ok so anyhow, what's the weakest link here? I'm guessing the best upgrades would be either the memory or the video card. What would be the best performance upgrade per dollar, staying under $200?

Vista?
Has it always been a problem? or just recent?

Nope, windows xp. It runs games ok on low settings, that part's not a problem. But he wants to be able to run some games on higher settings.

I am thinking this is the power savings of the CPU, try running a program and then running CPU-Z.  I am pretty sure it will then show 1.86.  My e6300 is OC'd but in idle/power savings it also shows 1.6

I would add another GB of RAM and an HD 3850 or HD 3870. Before doing that make sure the PSU is strong enough.

The biggest bottlneck is the video card. After that the ram would be holding this system back.

Add 1gb of  the same type of memory for $25.
Sell the 6600LE on e-bay for about $20.
Get a 9600GT for about $180.
 
Hope that he has an adequate psu.

yeah if this comp is meant to play games then your weakest link is the GPU. something like a HD3870 or GT/GTS would probably be the best for that system. but if you plan on playing games with a Core2 and any of the above GPUs your gonna want two or more gigs of RAM, prolly DDR2 800. and like previous posts said, the 6 multi is just a power saving feature.

I agree, new ram + gpu= gaming fun
2 gigs of ddr2-800, 9600gt good times

Hard Drive