1. I assume this is a sata drive, xp cannot be installed on a sata drive without sata controllers, which will have to be slipstreamed onto your xp install cd with nlite.
2. see here for 7b stop errors read through several threads and articles.
3. go here for install instructions, let me know if you do not understand any steps
4. this page is a search page for installing xp on an ACER
above talks of how to change ahci to ide, you can read and see for yourself, but you do not want to change really or you lose the benefit of a sata drive.