It's more likely that what you did is coincidental and not the cause.
You have a few options.
First, boot the system, start tapping F8, at the menu, select "Last Known
Good Configuration," and see if that resolves the issue. Since you were
able to boot, this probably won't work but it's worth a shot.
If the above fails, boot the system, start tapping F8, when the menu
appears, select "Safe Mode" and press enter. When you get to Safe Mode, you
should be presented with an option to go directly to System Restore, accept
it and try taking your system back to a time prior to when this began.
If that fails, return to Safe Mode as outlined above and see if you can back
up your user accounts as they may be corrupted. While the next step should
leave everything intact, better to play safe.
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.
