I would not/have not installed it...and won't do so until it's more than an optional download.
From what I see...those who have tried to install it...ran into more problems than needed when attempting such.
When it comes to MS.NET...I find that 3.5, SP1 takes care of XP needs on my system.
My advice would be...if you have a system where no program insists that MS.NET 4 be installed
...don't install it. The only reason I installed earlier versions of MS.NET is that certain programs required it to function effectively and they all made it clear during attempted installation...that it was required.
Edited by hamluis, 13 July 2010 - 12:40 PM.
Removed blank lines ~ Hamluis.