BSOD After Deleted Registry Keys

I followed these instructions in an attempt to get a new external hard drive to install on my HP xw4400 Workstation - Windows XP SP3.

----------------------------------------------------------
Important This section, method, or task contains steps that tell you how to modify the registry. However, serious problems might occur if you modify the registry incorrectly. Therefore, make sure that you follow these steps carefully. For added protection, back up the registry before you modify it. Then, you can restore the registry if a problem occurs. For more information about how to back up and restore the registry, click the following article number to view the article in the Microsoft Knowledge Base:
322756 How to back up and restore the registry in Windows

To fix this problem, delete the UpperFilters registry value and the LowerFilters registry value. These values may cause access problems. To do this, follow these steps:
Click Start, click Run, type regedit, and then click OK.
Locate and then click the UpperFilters registry value. This value is located in the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E967-E325-11CE-BFC1-08002BE10318}
On the Edit menu, click Delete, and then click OK.

Note If you receive an error when you try to delete the registry subkey, you may not have appropriate permissions to edit the subkey. For more information about how to set or change registry editing permissions, click the following article number to view the article in the Microsoft Knowledge Base:
310426 How to set or change registry editing permissions in Windows XP or in Windows Server 2003
Locate and then click the LowerFilters registry value. This value is located in the following registry subkey:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{4D36E967-E325-11CE-BFC1-08002BE10318}
On the Edit menu, click Delete, and then click OK.

Note If you receive an error when you try to delete the registry subkey, you may not have appropriate permissions to edit the subkey. For more information about how to set or change registry editing permissions, click the following article number to view the article in the Microsoft Knowledge Base:
310426 How to set or change registry editing permissions in Windows XP or in Windows Server 2003
Exit Registry Editor.
Restart the computer.
Note If you remove both registry values, and then you lose functionality in a particular program such as CD recording software, you may have to reinstall that software. If this problem occurs again, contact the software vendor for help.
----------------------------------------------------------------

I created a restore point, but not a back up disk prior to deleting the registry keys. However, I can't even get the computer to boot up in Safe Mode or Last Configured Setting.

Is there anyone who can help with some options? I have access to the Bios menu, as well as the HP Back Up and Recovery Console, but nothing else works.

I'm desperate, as I have a lot of media and programs on this computer that I need access to. Re-installing Windows XP Professional is not an option if I'm going to lose all of that information.

Any and all help is greatly appreciated. Thank you!