Burn a Debian 64bit or OpenSuse 64bit CD and try.
This is what I would do.
I had a look at the Pentium D and it should be similar to Pentium 4 ? (a guess).
So my recommendation would be: use a low RAM system (lxde or others).
Perhaps an Antix 64bit would be the good choice (I have an Antix 32bit on my Pentium4 with 3GB RAM).