How to Display the items in listbox in windows phone 7?

please tell me how to show alphabets at the right most of list whenever click on particular alphabet i need to show that starting words.

tell me how to acheive this.

What you are describing is very iOS-like. The more appropriate experience for WP is the same as the contacts list uses (and application list if it's long enough), whereby each "group" contains a header icon above it and tapping that icon provides a selection of all of the group headers (letters in your case).

The LongListSelector control that ships as part of the Windows Phone Toolkit does all the legwork for you, you just need to supply it with a list of groups. For your case, I'm sure OriginalList.GroupBy(x => x.Name[0]) would be sufficient for ListListSelector.ItemsSource.