A DOS boot disk is useless if your files are on a partition that is
formatted NTFS which is why you are getting the "Invalid Drive
Specification" error. You might try accessing your files in Safe Mode.
Boot the system, start tapping F8, at the menu, select Safe Mode and press
enter. If you can get into Safe Mode, you should be able to recover files.
If you cannot get into Safe Mode, there's till hope. Assuming your system
is set to boot from the CD-ROM drive and you have an
actual XP CD as opposed to a recovery CD, boot with the XP
CD in the drive and perform a repair install as outlined below. If the
system isn't set to boot from the CD or you are not sure, you need to enter
the system's BIOS. When you boot the system, the first screen usually has
instructions that if you wish to enter set press a specific key, when you
see that, do so. Then you will have to navigate to the boot sequence, if
the CD-ROM drive is not first line, set it first in the boot sequence. Save
your settings and exit with the XP CD in the drive. The system will reboot.
NOTE, while a repair install should leave your data files intact, if
something goes wrong during the repair install, you may be forced to start
over and do a clean install of XP. If you don't have your data backed up,
you would lose your data should that eventuality occur.
Boot from the CD. If your system is set to be able to boot from the CD, it
should detect the disk and give a brief message, during the boot up, if you
wish to boot from the CD press any key.
Once you have pressed a key, setup should begin. You will see a reference
asking if you need to load special drivers and another notice that if you
wish to begin the ASR (Automatic Recovery Console) depress F2. Just let
setup run past all of that. It will continue to load files and drivers.
Then it will bring you to a screen. Eventually, you will come to a screen
with the option to (1) setup Windows or (2) Repair Windows Installation
using the Recovery console.
The first option, to setup Windows is the one you want and requires you to
press enter. When asked, press F8 to accept the end user agreement. Setup
will then search for previous versions of Windows. Upon finding your
version, it will ask if you wish to Repair your current installation or
install fresh. Press R, that will run a repair installation. From there
on, follow the screens.
If you only have a recovery CD, your options are quite limited. You can
either purchase a retail version of XP will allow you to perform the above
among other tools and options it has or you can run your system recovery
routine with the Recovery CD which will likely wipe your drive, deleting all
files but will restore your setup to factory fresh condition.
If this gets you back into your setup, for future reference, just remember,
first rule of "safe computing" is "Make Good Backup."
