There is a file in C:\windows called "windowupdate.txt"
This file dates the first time windows was updated on the computer.
Most people will update as soon as the fresh OS is installed.
Hopefully this will be the same for you.
And will be good proof as to when the OS in question was installed.
windows update would have nothing to do with which browser he uses (Firefox or IE Explorer). It has to do with your Windows system updates that you do. As said above, most new installs of XP will be out of date as far as security updates and such. That means that it will usually start asking for updates the first time it finds an internet signal on that PC. So unless you turned off automatic updates, or just ignored them when the yellow shield icon poped up, then your first update should be within a few days of when you installed XP.
SIW (Systems Information for Windows) will provide this information - look under Operating system or installed programs to get first installation dates (SIW is a free download)
