It would help if you could reply in complete sentances.

I don't know which setup is which....
As to DHCP and clashing addresses. You are kind of correct, DHCP will not issue a clashing address. But when you are also using static address, then it _can_ issue out that same number if you have not correctly adjusted your DHCP pool to avoid conflict.
Put this another way.....
I would expect your IP Addresses to be as follows:
Router: 192.168.11.1
MainPC: 192.168.11.2
MCEPC: 192.168.11.3
All with a subnet mask of 255.255.255.0
The two PCs with a gateway of 192.168.11.1
The two PCs with DNS settings of 192.168.11.1 and 205.188.146.145
Note how all three machines have the same set of numbers at the start of the addresses? This is the "network" part of your address.
Also note how the last number is different for each PC? This is the machine part of the address.
If you are using DHCP, then you will find that you have a choice in the router to set the size of the DHCP pool. This is the list of addresses that the router hands out. You need to make sure that this pool does not overlap with any of the static addresses you are setting up.
So if you are setting up static addresses of "192.168.11.19" and "192.168.11.20", then you need to make sure the DHCP pool does not include these addresses. For example, set the pool to 192.168.11.100 to 192.168.11.150 as this allows for 50 PCs to be added to your network, but all staying away from the addresses of your current PCs.
In fact, it is much easier to EITHER use DHCP on everything, or to use Statics on everything. Mixing it causes the confusion you are getting.
