unmountable_boot_volume error

Hello,

I have a sony vaio laptop vgn-sz220 with xp. When starting my computer, I get the blue screen of death with a unmountable_boot_volume error. I tried running it in safe mode or in the last known good configuration, but when all of the drivers are loading up in the black screen it stops at windows/drivers/tdi.sys.

I tried booting it from the xp boot cd I downloaded, but when I am in BIOS, there is no option to boot from cd or dvd rom.

I contacted sony technical support and told me to run the recovery unitlity wizard that is loading into all sony vaio laptops. But, when I run the recovery utility wizard, it only loads like 1/8 when i get the following message:
file setupdd.sys could not be loaded.
the error code is 4125.

setup cannot continue. press any key to exist.

I do not want to run the recovery cds because I have very important files on my hard drive.

Any suggestions on how to fix it or at least retrieve my files??? Any help will be appreciated.

Thanks