Control panel, system, general tab.  However, what you probably want is
the Product Key as that is what is used for installation.  If so:

The W98 ProductKey is generally found on the Windows user manual, the
certificate of authenticity, a sticker on the PC, or the sleeve or jewel
case the Windows CD came in.  The Key also might be available from the
system.

If the system is working in either safe or normal mode:

Open regedit.exe to this key and look in the right pane for the entry
ProductKey:

HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion

If the system is not working, start the computer with a floppy startup
disk.

At the A: prompt, type:  C:\Windows\Command\Find /N "ProductKey"
C:\Windows\System.dat
(Note:  ProductKey must be typed in upper and lower case letters as
shown and there is a space after:  "Find"     after:  "/N"    and after:
"ProductKey"

If the hard drive has been formatted, contact the maker of the computer
if W98 was provided with the computer.  If it's a retail version of
Windows, contact Microsoft at:  1 800 426 9400.  I doubt you will have
any luck with these final two options however.  You can also try a
search on Google to see if you can find one.

RIGHT CLICK ON MY COMPUTER LEFT CLICK ON PROPERTIES