How to format when os in hard disk?

I using Windows XP in my PC. So i need to change my OS XP into Windows 7 but it is in my Hard disk. Please help me how can i format my PC when OS in Hard disk?How to format when os in hard disk?
Hav u lost ur original disc or its just 30 days trail image u hav downloaded???



As u dont hav it in a disc so u will not be able to install ';Microsoft Windows 7'; by booting ur PC....The only option u hav is to run the setup from ur existing windows (';Microsoft Windows XP';)



Now all u hav to do is run the setup.If u hav the disc image then mount it on a virtual drive.If u dont hav any virtual drive then download ';Daemon Tools'; - http://www.daemon-tools.cc/downloads/dtp



Now mount the image on ';Deamon Tools'; %26amp; close the Autorun Menu...Now open ';My computer';, right click on the virtual drive (Windows 7 Disc) %26amp; select open....Copy all files in a folder %26amp; run the Setup (SETUP.EXE)....

Now select ';Upgrade'; to install it over ';Microsoft Windows XP'; - http://www.freeimagehosting.net/image.ph



U can also select ';Custom (Advanced)'; installation %26amp; when the partition selection option will come click on on a different drive to keep both the OS (';Microsoft Windows XP'; %26amp; ';Microsoft Windows 7';) - http://www.freeimagehosting.net/image.ph



Now if u hav all the files in a folder just open the folder %26amp; run the file named ';SETUP.EXE'; %26amp; rest of all r the same....



Now if u hav a image u can also burn it in a DVD to enable the ';Boot from DVD'; feature. Then insert ur ';Microsoft Windows 7'; disc into ur optical drive (DVD Drive) %26amp; boot from it by restarting ur PC.......How to format when os in hard disk?
you can upgrade your xp to 07.
Hi friend.you want to change booting device in CMOS/BIOS setup. now it may be the boot from cd drive but you have to change.

first boot device should be hard disk

second boot device should be cd drive



%26amp; save your configuration what you have changed %26amp; restart the system.

now your windows 7 in hard disk will detected %26amp; boot

afterwards you follow the instruction %26amp; install.