I have replaces the HDD on an aspire 3502 laptop and every time I install the recovery disks, it will allow me to get to the very end of the install where it says Recovery complete, remove disk and reboot computer. When I do, I get the message "OS not found". I can't remember if the recovery disks came with a separate windows xp disk or not but at no time during the recovery install does the system ask for the windows product key. The old HDD is useless for any information on the partioned part of the drive. The machine will not do anything with the old drive installed. Any help would begreatly appreciated.