>>>>no username
>>>>password is Admin
>>>
>>>Darn. I did use something other than Admin. At least I should learn to write those things down somewhere within my reach <g>.
>>>
>>>Thank you for your help.
>>
>>try
>>admin
>>...all lower case
>
>I did, no luck. I seem to remember creating a user name and password, but don't remember writing it down. It always seems to easy to remember when you create them <g>. I think there is a reset button on these routers so I will have to reset it. I will probably lose my DSL modem information, right?

Yeah there is a reset button. You have to hold it in for a few seconds until you see the lights on the front flash a few times.
As for the DSL modem info, yes you're going to loose that and any ports that you have forwarded will be lost too.

Now, to prevent the problem you were having to begin with.....
If someone has logged into your router and is using your connection - if they used DHCP to do it, then yes, you can look at the DHCP table in the router and see the extra machine. If they gave themselves a staic IP address, then you won't be able to see them this way.

Best things you can do:
Setup encription (don't use the WEP one, use the other one (I think its wpk))...
Turn off DHCP, assign all your computers static IP addresses. This also helps when you start forwarding ports.
Limit the number of computers that can connect to your router to the number of machines you have.

...Really just setting up the encryption will probably keep the others off it, and it won't slow you down enough to really notice.