EDIT: I missed the Media Center part

, and I don't have a way to verify the post below, so I hope I did not get off on some wild goose chase - my commentary should work for XP (this is the XP forum

)
You really should get hold of a boot CD, but...
Why not just run msconfig in Safe Mode and uncheck the /SAFEBOOT option?
If all you did was boot normally and then run msconfig and check the /SAFEBOOT option on the BOOT.INI tab, that just adds this to your current boot.ini file:
/safeboot:minimal (or /safeboot:something...)
to the end of the [operating systems] first multi choice line, so why can't you boot in Safe Mode, edit the boot.ini file, remove the /
safeboot:minimal part, save the boot.ini file, reboot in normal mode?
The boot.ini file is going to be in C:\ and will be hidden and read only, so in Explorer you need to navigate to C:\ and click Tools, Folder Options, View.
Check - Show hidden files and folders (so you can see the hidden files)
Uncheck - Hide extensions for known file types (so you can see the .ini extension)
Click OK
Locate the boot.ini file (first make a copy for safety), right click the boot.ini file, Properties, uncheck the Read-only box, OK.
Now you can use a text editor to edit the boot.ini and remove the /safeboot:minimal (or /safeboot:whatever it says), save the file and reboot in normal mode.
If you are not sure it looks right, copy and paste the contents of your boot.ini file back here.
When you are finished testing, change the boot.ini back to read only and undo your changes in Explorer if you feel like it.
Here is a generic boot.ini file
without the safeboot:minimal stuff in it.
[boot loader]
timeout=10
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Microsoft Windows XP Professional" /fastdetect /NoExecute=OptIn
C:\CMDCONS\BOOTSECT.DAT="Microsoft Windows XP Recovery Console" /cmdcons
With the safeboot stuff it looks sort of like this:
[boot loader]
timeout=10
default=multi(0)disk(0)rdisk(0)partition(1)\WINDOWS
[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="XP Professional" /fastdetect /NoExecute=OptIn
/safeboot:minimal
C:\CMDCONS\BOOTSECT.DAT="Microsoft Windows XP Recovery Console" /cmdcons
Yes, you still should come up with a bootable CD, preferably a bootable XP CD, but the other offerings will be good if you can't come up with that.