This is a bit of a "long shot" but the sites you cannot access may have been blocked by an entry in your Hosts file (nothing to do with the "host" PC) in Windows 98.
Have a look for a file called Hosts or Hosts.sam in C:\WINDOWS\ and open it with Notepad. The default file would normally have only one entry in which is:
See if there are lines in there for:
and if so, delete them, save the file and exit.