[CentOS-docs] Wiki improvement

[Ron Arts]

Hello list,

I found an error on the page http://wiki.centos.org/HowTos/InstallFromUSBkey,
and I wanted to fix it, but appararently I need to follow this procedure.
The error is you need 20mb on the USB VFAT partition in stead of 10mb
for the latest CentOS 5.x releases.

My wikiname is RonArts.

Thanks,
Ron