dlg.exe is a part of BVRP Phone Tools software suite. It offers faxing, phone book, e-mailing and more.
This is a non-essential process so disabling or enabling it is down to user preference.
NOTE: The makers of this utility have also made SpyWare in the past. To-date, dlg.exe is not classes as spyware however.
Non-system processes like dlg.exe originate from software you installed on your system. Since most applications store data in your system's registry, it is likely that over time your registry suffers fragmentation and accumulates invalid entries which can affect your PC's performance. It is recommended that you check your registry to identify slowdown issues