When I click on turn off computer the shut down screen is shown in classic mode. How I change it into default mode?

Am not sure what you mean by that but I think I know.

Reset your BIOS to default or optimal settings and enable Advanced Power Management support

1. Click Start, click Control Panel, and then double-click Power Options.

Note If you are using Windows XP, click Switch to Classic View in Control Panel to more easily follow these steps.
2. Click the APM tab.

Note If you are using multiple monitors, the APM tab may not be available.
3. Select Enable Advanced Power Management Support, and then click OK.

Hope this helps...

Cheers