It doesn't mean nothing.
You asked to upgrade to a Pentium Dual Core. You said you have a Pentium D 930. You already have a dual core.
You also said you cannot upgrade to Core 2 Duo. The E2180, although being called Pentium, is based on Core 2 Duo architecture. Thus, any technical problems you may have with upgrading to a mainstream Core 2 Duo will also be had with the E2180. If the inability to upgrade to Core 2 Duo is merely a matter of cost, then go ahead and the get the one you want. A good overclock will make you happy for at least two years.
However, I just went and looked at the 945P chipet. According to Intel's website, it does support Core 2 Duos. Therefore, you should buy the one you have linked to. It will trash your old dual-core.