I wanto to reformat my laptop acer aspire4220

Yes you can provided you have the necessary Recovery Disks. if yes then go ahead. if you use the Recovery disks, then in any case the OS will reformat the HDD and then install the OS. If you do not have the R disks then also you can install the OS from normal Windows (meant for PCs) but you will loose the use of Fn key and whatever functions it does, the use of WiFi. If you can afford to loose it then by all means do the needful. There is a way out. After installing (PC) Windows, XP or whatever, go to the site of Acer and down load the drivers for the use of various components of the laptop and install them. A long drawn affair. The choice is yours.

Put bootable cd in your computer driver and then restart your Pc.