I had to shut down my Hp laptop by unplugging it and taking out the battery. now the laptop will not boot up. It tells me that windows did not start successfully and to choose last known configuration but it does not work. I even tried rebooting in safe mode nothing. How can I get my laptop to work?

"...last known configuration but it does not work. I even tried rebooting in safe mode nothing...." Can you clarify that first (please)? Does it fail to actually boot after you try last known good config; and/or does it fail to boot into safe-mode? If so any error messages etc.? Why the need to switch off by removing power source(s)? What do you see on the screen first when laptop powers up? Do you have an XP CD - ideally a Full version - or at least an Upgrade version; or only a dreaded recovery disk?