@ priyankashah - if you are interested in using and trying win 7 why not get a trial version from here
Download Windows 7 (SP1 Included) Free Trial - Performance, reliability, security, and compatibility are core tenets of this release - Softpedia
it comes as a iso file with SP1 included - so just write it on a DVD to make a bootable DVD or create a bootable USB install media using wintoflash.
If you don't need ubuntu just delete all partitions and create a new partition for win 7 ( the win 7 bootable media you give you options for that ) and install win 7 there but before installing win 7 make sure your laptop has proper driver support for win 7.
Download Windows 7 (SP1 Included) Free Trial - Performance, reliability, security, and compatibility are core tenets of this release - Softpedia
it comes as a iso file with SP1 included - so just write it on a DVD to make a bootable DVD or create a bootable USB install media using wintoflash.
If you don't need ubuntu just delete all partitions and create a new partition for win 7 ( the win 7 bootable media you give you options for that ) and install win 7 there but before installing win 7 make sure your laptop has proper driver support for win 7.