BHO.dll is a "Browser Helper Object" and may or may not be legitimate.
Run a spyware and an antivirus program if you have not already done so.

yes you might have deleted something, or you uninstall a particular program and also deletes that particular file but other programs might be using it..
try this: go to start->run-> then type regedit press enter.. then at regedit window click on Edit->Find-> then type "BHO.dll" then delete the keys that it will find..

But if you're not familiar with Registry Editor don't do this please. you might messed up your whole system.

Maybe there's some other ways to solve this.

Hi,
Do not touch your registry before you back it up!!!
If you do not know how, search the net!!!

@ sparkx:i run the spyware and anti virus yet still the error exist...
@ cguan_77: so sorry this is my firts time to try registry editor so im not familliar on it!! can you suggest a safer try??

try this site-
http://www.novell.com/coolsolutions/tools/18177.html

Hi again,
The best anti-virus program will not get all viruses. Go to this site:-
http://www.daniweb.com/forums/thread27570.html
Read about deleting viruses and checking your PC including virus checkers you can load from a boot-up.
If you follow all the suggestions here, even if it has not fixed your PC, you will at least know that it is not a virus or malware that is causing the problem.

Hi again,
After you have rechecked for virus's and malware, try doing a SFC just to ensure your Windows files are OK.
Sometimes, some of the windows protected files can be lost or changed. To detect any problems run the program “System File Checker” (SFC). Before you run it you should purge your PC’s cache:-

Go to “START”
Click “RUN”
Type or “copy and paste”.. sfc.exe /purgecache

Note:- the space after “exe”.

The “purgecache” in this command will empty the cache before you run the file checker. You should always purge the cache before scanning with the System File Checker (SFC). That way, you can be sure that system files are copied from your Windows installation media, and are not infected with malware or corrupted. After the cache has been purged, run System File Checker.

Go to “START”
Click “RUN”
Type or “copy and paste”… sfc.exe /scannow

Note:- the space after “exe”. You may be required to use your installation disk.

This could take a long time to complete, when finished, reboot and see if the problem still exists.

Maybe you delete something in mistake, I guess you can use some registry tools to solve this problem.
Or why don't you reinstall the program if you know which program you deleted?

The registry tools you offered cost $30,00...
Did you mean that he may have deleted a file by mistake?
If he deleted it by mistake, it would still be in the recycle bin, (if he has not emptied it) and he just needs to restore it, not reinstall.