|"I have removed the battery overnight and did the cmos jumper reset but still the same problem"|
If you do it right, you can reset in a matter of seconds...you do NOT have to leave the battery out overnite. Since you reset the BIOS, did you correct all the settings? Since it's a Dell, I'm sure they're not too complex.
All you really needed to do was use a password recovery program but since you attempted to reinstall XP, that approach probably won't work anymore. Boot off the XP CD, delete ALL partitions, create one (or more), format them as NTFS (full format, not quick), then try the reinstall again.