when yahoo messenger chatting people can able to accessing my coumuter files is it?

Your best source for information on this sort of thing is always going to be an internet search.

Use a search phrase like yahoo chat hack, which found this[^], amongst thousands of other hits.

Sorry answerers I not getting correct sites from internet. I little feeling messenger being open at hackers because I reading some sites saying yes but what yahoo mail chat being safetyful? I not getting that information.

I not programming man and please helping myself. I joining this site to asking because I feeling this site being better like one programming man suggesting and not others like rediff and all.

I fearing doing business because other tenders and purchase orders and etc will showing to peoples I chatting.

It's not totally impossible. Chat clients have been known to have vulnerabilities in the past, and both Yahoo and Live messenger have been hacked (or cracked) remotely using buffer overflows, which means if someone discovers a vulnerability, and that someone is in your buddy list, he/she can possibly execute code on your machine. Chances are quite low that anything like that would happen though.

Also on Vista and Windows 7, the chat client will be running as a normal user and so even if a buffer overflow based exploit exists, the remotely executed code will not be running as a privileged user. That said, even a non-admin user can still read a lot of files on your desktop/documents folder/pictures folder etc. Once again this is a low probability scenario but since you seemed to be more curious as to the practical possibility of such a thing than worried about it actually happening I thought I'd throw in my bit.