Right, I've managed to locate the manual for your laptop and you are right - there is no boot sector virus protection by the looks of it!
Going back to your original post, you said you get an I/O error message. I assume this is when you attempt to boot from the hard disk with NO floppy disk or CD inserted, right?
Have you tried booting from a bootable floppy disk instead?
If you require a floppy boot disk, you can download one from this link :http://freepctech.co.../files010.shtml
Make sure you download the MS Windows XP System Setup disk (single disk option). Once downloaded, just double click on this file, insert a new or known good floppy disk and it will create the boot disk for you.