the os is vista home premium.Actually the cd-rom is not able to detect the dvd ,but when i use cd it works prefectly.I tried very much with diffrent disks but its not responding.somebody was telling me it's the lens problem.
Maybe there's a factory mistake and you're given a CD-rom instead of DVD-RW ? Check it. Anyway you must call service centre of your area (try to find out that at the place you've bought laptop) and they will either fix it or replace.
Maybe it's an OS gluck (bug) - try recovering by NOVA. Don't touch lens.