another problem is i dont hav a cd/dvd drive in my lap.can anyone please help me to solve this by booting from my pen drive.
Assuming you have a bootable Linux on the pen drive,
1) with the laptop turned off, plug in the pen drive.
2) turn on the laptop and edit the BIOS boot menu to poll the removable drive for a bootable OS before polling the hard drive.
3) save and quit the BIOS.
4) it should boot the Linux on the pen drive.
5) once Linux is up and running, you can then recreate the Linux partition and reinstall Linux in that's what you want to do.
Otherwise, you will need to repair the MBR to boot into windows. Without a cd drive and windows recovery disk, I don't know how you would go about doing that.