2.46+ trouble

I don’t know if this is the right place for this but i think this is a troubleshooting forum among other things so…
I don’t really speak english but here goes:

I love blender ! It really made 3d an enjoyable experience for me and i’ve been using it since version 2.42 but when it reached version 2.46 (the one with all good fresh features …)
It freezes like almost everytime i do a render bigger than 400px300px using the new features and stuff.
Then I downloaded 2.47 and same goes…
My pc is not brand new (single core intel P4 3,0ghz 1,5gb ram | windows xp sp2) ,but i can do a lot of things with it.
But with this trouble i’m still in version 2.45 which is VERY stable but, i really would love to use the new features.
Is it my hardware???
Forgive me if that’s the wrong place to post it and feel free to delete it.