Really I think you should be ok you have erased all your files and that should be sufficient. If you reformat the computer you will need to reinstall 98 and possibly run into problems there. Keep in simple. Maybe a way to put a log in pass word on 98 so only your sister in law knows it..

If you really want to me sure everything is gone, you could image the drive, then use something that will securely delete the contents, then restore the image. There are a number of programs that are available for free to do these tasks.

If you're just concerned with the garden variety user snooping for data, you could delete your files, then go into the recycle bin and empty it, then run the disk defragmenter. That would protect it against most people.

I deleted and uninstalled everything, emptied recycle bin and defragged.

thanks

Use the following

Here is a link that might be useful: DBAN

"Use the following

Here is a link that might be useful: DBAN"

That's one of the programs that I had in mind if you want to securely erase the drive. If you plan to do that, you'll need to either image the drive after deleting what you want, then restore the image after running dban or you'll need to reinstall the OS from original CDs (do you still have them?).

since you have already done what you decided to do I would most definitely set her up as Administrator on the pc and set up a user name and hard password for the pc so that anyone there can not access it they would have to know her name and password to enter the pc.
Other wise they can just sit at her pc and do anything and that leads to infections and she does not need that.
Be sure you load some of the good free antivirus programs on it like AVAST which does work on 98 and malwarebytes free, make sure she knows how to update and run scans. I would also put spywareblaster free on there and show her how to hit the update button once a week on it and then hit the enable all protection no scans to run it just runs in the back ground.
I would also install firefox on it and have her use that instead of IE.

The computer won't be online and isn't connected to the internet now. The computer will be used to play an old version of solitaire and that is it.

My sister in law has ongoing memory loss from a brain injury and can't remember a password or how to logon to the computer. She also can't type due to physical deformities of her hands from the same injury and is in a wheelchair. (a drunk driver hit her) This injury occurred back in 1980 and she doesn't even know what the internet is. Her memories are mostly from her childhood.

I do have the Windows 98 disc that came with the computer.