Johnboyxp

If you have the Vostro 220 Mini Tower version, the following are compatible,

Yorkfield Q8400 2.66GHz
Yorkfield Q9400 2.66GHz 
Yorkfield Q9550 2.83GHz 

Prior to installing the processor, you need to upgrade the BIOS to latest version, as support for new Intel CPU's was added with version 1.2.0.

Bev.

I am looking to upgrade a Vostro 220 (motherboard OP301D) and a Vostro 200 system.  Whch quad core processors will they take?

Johnboyxp

Only the Vostro 200 Mini Tower supports Core 2 Quad procesors.

Vostro 200 with a G33M02 motherboard and a 300w PSU, only support dual core processors. 
  
If your Vostro 200 MT has G45M03 motherboard and a 350w PSU, then the following Core 2 Quad CPU's are supported,

Yorkfield Quad Core Q9400, 2.66G, 6MB, 1333FSB, R0
Yorkfield Quad Core Q9550, 2.83G, 12MB, 1333FSB, E0

Intel Core 2 Quad Q8200 (2.33 GHz, 1333 MHz FSB)
Intel Core 2 Quad Q6600 (2.4 GHz, 1066 MHz FSB)
Intel Core 2 Quad Q9300 (2.5 GHz, 1333 MHz FSB)
Intel Core 2 Quad Q9650 (3.0GHz, 1333 MHz FSB) 

Prior to installing the processor, you need to upgrade the BIOS to latest version 1.2.4, as support for new Intel CPU's was added with version 1.2.0.

Bev.