If you do the following before upgrading from Windows 98 (W98) to XP, you may be able to continue using your old W98 applications after installing XP, without re-installing the old applications under XP.

1.) Consider KernelEx to run Windows XP applications on Windows 98.
2.) You will need a separate drive from the one containing W98. For example, if W98 is installed on C:\ then you will need a D:\ drive. Either install a new drive D:\ in your machine or use an external USB drive D:\
3.) Copy the contents of the old C:\ drive onto the D:\ drive. Ignore and folders that cannot be copied because they are in use during the copy operation.
4.) Install XP on the old C:\ drive.
5.) Go into the directory on the D:\ drive where your old W98 application exists and try to execute it.

[Via Wikihow]