Forgot my specs:  Dimension 8300, Windows XP SP 2. 

Last time this happened to me the Network Connections service was not running.  Try to do it the easy way first.  Click Start, Control Panel, Performance and Maintenance, Administrative Tools, Services.  Look for Network Connections; first, note whether or not this item is present.  On my problem this was completely missing.  If it is present, note its status.  It should say "Started".  If it says anything else, double click the line to bring up the properties.  In the middle of the box you should have a field labeled Startup Type.  Use the menu to put "Automatic" in the field, Apply if the box is available, and then OK out of the function.

 

If Network Connections is present and started your trouble is different from mine but possibly related.  If it is totally missing the only fix I know of is a direct registry change.

 

Just check the Firewall service to see if it set to Auotmatic.  If not, then you either had another Firewall program running at some time or some spyware has turned it off.

Thanks, guys.  I checked, and Network Connections was started but set to manual (I changed to automatic).  I also tried to start the Firewall from there (it shows disabled), and I got this message:

 

"Could not start the Windows Firewall/Internet Connectiion Sharing (ICS) servie on Local Computer.  Error 1068:  The dependency service or group failed to start."  

 

Thank you, Jack.  I'll follow Microsoft's instructions.  I've also resorted to the HijackThis forum, so perhaps they can help me. 

You're problem is not the same as mine, regrettably.  Microsoft has a list of other things to check on this error here.  If you already have a connection set up you shouldn't need to perform the step regarding using the Connection Wizard, but on the other hand, the Wizard may be the only process you can use to get your connection back.