If you were using 98Se that mean you had a FAT partition.
If you chose to upgrade the partition to NTFS, then the
installation formats your HDD, causing you to lose all
your data.
If you stuck with the FAT partition, do a search for all
text files and see if any documents you created appeared.
Next, if no documents appear, check to see if your
programs that you had installed on WIN98 are installed.
If not, this means you probably selected an option for
format your hdd. If your programs are still on your
Pc...then comb through every file on your hdd very
carefully.