stealth.wm.exe is a process which is registered as PE_THEALS.A Worm.
"This virus is distributed via the Internet through e-mail and comes in the form of an e-mail message, in the hopes that you open its hostile attachment. "
The worm has its own SMTP engine which means it gathers E-mails from your local computer and re-distributes itself.
"In worst cases this worm can allow attackers to access your computer, stealing passwords and personal data. "
This process is a security risk and should be removed from your system.
Non-system processes like stealth.wm.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