then I would uninstall it. Hopefully there is a System restore point you can go back to a date before Spybot was installed, and I would try that rather than the normal uninstall method. if you cannot get into Windows normally, try booting into Safe Mode. Just press the F8 key once a second after the initial BIOS boot screen until the list of Safe Mode options appear. Then choose the top option and press Enter.
If you can get to the Safe Mode list of options but cannot load Windows, reboot into Safe Mode and try the option "Last known good configuration".
Does this system have AVG8 by any chance? It is Grisoft's replacement for AVG7 anti-virus. I ask because there has been mention that AVG8 breaks Spybot.
If that works, I would download MalwareBytes and SUPERantispyware and run those separately to search for and remove any spyware.
I am having a problem booting up every since I downloaded spybot from here,once booted up I get a popup of a black screen that has c\windows\system32\command and another screen that says the parameter is incorrect, and it will not let me go any further, I am running Windows XP home edition on a Dell Latitude laptop with service pack 2, I need help now because this is some elses computer that I was trying to get all the spyware off of but something went wrong in the process.