PC2-3200R in PE1950 possible?

Hi all,

I found some gigs of PC2-3200R DDR2 ECC REG Ram. But I've in mind, I can only use 4200 or 5300.

Is that right? Or can I put my 3200 in (with a Little loss of performance)?

If not, which ram can I use? Does it have to be ECC? Or will "normal" Desktop rams work?

Thanks for help and sorry for silly questions in bad english ;)