Well, we could make sure it is not a virus or spyware...As I think MWSBAR.DLL is part of the MyWebSearch infection.

Download hijackThis. Extract it to its own folder. Then run it and select. Do system scan and save log. Post the contents of the log that pops up.

Here is good suggestion for u to completely remove that kind of error during startup
please follow these instructions.....
1.click start menu ----> click run -----> then type "regedit.exe"
2.expand the registry to
"HKey_Local_Machine\software\microsoft\windows\currentversion\shareddlls"
then in right pane look the path or dll file which u get error during startup
and delete it and then restart the system