the old (hitachi - hdd was with an Acer aspire tho still unsure of bios or where to look for that !,it was with this intel celeron cpu 550@2.00Ghz 2.00Ghz memory 1Gb system type:32 -bit operating system vista service pack 2 this all failed in an 5315 the hard drive loaded but everything would fail or just slow itself to a blunt repetitve stop.,so on replacing it with samsung i need to know why i cant change the operating windows from vista to xp with a setup disc i iso . replacing the hdd is fine and the setup works but after a few minutes of loading files it sais it cant find hard drive at all . though, i know when i enter setup it sais 500gb hard drive !HeLp pls the os is not recognising this new hard drive so ...i can tell when the find is true because the hard drive(external) i tried is found and will allow the installation, tho, this finds me to want a partition i know i wont format the hard drive(external) so...it looks like the BIOS is not supportive!ahh will take it to cex where i bought it but thanx for your help emerald