If you're using Windows 2000 or XP this should be Disabled to stop "hacker" attacks from gaining access to the O/S.
Its not needed for a Home User at all, only if your on a company shared network at work.
So to disable this it could already be set by a Windows Update that might have fixed it, but you never know unless you actually look to see that it has been switched off to keep the PC safe.
You must have Administrator Rights!!!
So you look in the Registry Key
where it says EnableDCom Y then you have to change it to N (NO)
Right click on this and Select Modify, then type in N
just like that 1 letter.
Then close out the Registry and re-boot Windows.
After this then go to Start, Run, type in the box dcomcnfg
now you should see a dialog box, go to the second tab Default Properties and
UNCHECK = Enable Distributed COM on the computer. Click Ok and exit.
Now it will no longer be runnning in the background and unused Ports will be closed off when on the Internet.
Microsoft Article that explains this: http://support.microsoft.com/kb/825750