When I started the system it shows that ntldr is missing.
Press ctrl+Alr+Del to restart.
I installed Windows Xp freshly and again after some time when I restart the system it shows same error..
Can any one suggest me to solve thisissue without reinstalling os(Windows XP).

Check this out: Simple "ntldr is missing" fix with boot floppy, CD-R, or USB flash (http://tinyempire.com/notes/ntldrismissing.htm)