No version of Unity 3D working...

So i tried the latest one (4.1 i think) first, then the 3.5.7, then the 3.0 (first of all versions) and only the 3.0 worked. The thing is, i install it, all goes well, then when openning, even if running as administrator, it shows me the "Send don't send" error and i can't run Unity 3D. The 3.0 version worked, but it's so outdated that i don't feel that confortable using it... Im not new to moddeling, nor texturing or even programming (Python and C), and i just wanted to be able to build my own game, and get more programming and modelling and texturing experience, because i know this will influence my future, so i never gave up on Unity 3D, i've been doing this for about half a year, couldn't ever get Unity to work

I meet all the requirements CPU is a AMD Athlon 2.4 @ 2000 MHz GPU is an Nvidia GeForce 6600 with 256 mb 1 GB RAM Runnig XP SP3 32 bit have everything up-to-date so i really don't know what could be wrong... please help me, i'd really love to finally start using Unity 3D

Thanks in advance