I well take u step by step to how burn
ISO or NRG Files
After downloading all parts for XP or Vista
or any ISO file do this
and u well get something like that but with different name ....Right
then Download Ultraiso v8.6.6 build 2180 premium edition
http://www.mediafire.com/?z0uuyeyyjc3
OR
http://www.zshare.net/download/12071423c6657d41/
Now....double click to open iso file in Ultraiso
and choose Burn Image Button
Choose good speed for burning
after u finish burning ISO file
it well automatically extract on CD or DVD
Dont forget to use Blank CD to burn XP or any iso file
less than 700 MB
and use Blank DVD to brun Vista or any iso file
more than 700 MB like Vista its 2.8GB
Then put cd and restart ur pc
to install fresh copy
Have fun
See My Amazing Post for 100%Original Copy of Vista SP1