You can make pen drive bootable manualy without any software.
You need a 4gb pen drive.This trick works only in win7/VISTA os to make pen drive bootable for the installation of win7/vista.
You have to follow the following steps to make your pen drive bootable.
step 1: Format your pen drive
1. Plug in your USB Flash Drive
2. Open a command prompt as administrator (Right click on Start > All Programs > Accessories > Command Prompt and select “Run as administrator”).
3. Find the drive number of your USB Drive by typing the following into the Command Prompt window:
The number of your USB drive will listed. You’ll need this for the next step. I’ll assume that the USB flash drive is disk 1.
4. Format the drive by typing the next instructions into the same window. Replace the number “1” with the number of your disk below.
select disk 1[enter]
create partition primary[enter]
select partition 1[enter]
Step 2: Make the Drive Bootable
1. Insert your Windows Vista / 7 DVD into your drive.
2. Change directory to the DVD’s boot directory where bootsect lives by typing the following commands In the same command promt (here "d:" is my dvd drive):
3. I’m assuming that your USB flash drive has been labeled disk G: by the computer:
bootsect /nt60 g:[ENTER]
Step 3: Copy the installation DVD to the USB drive.
After you’ve copied all of the files to the disk. You are ready to boot from pen drive.
Step 4: Set your BIOS to boot from USB
This is where you’re on your own since every computer is different. Most BIOS’s allow you to hit a key at boot and select a boot option.