There are two safe solutions.
Solution one, is to upgrade the outlets properly to comply with all recent electrical codes, which means that they should have a ground and GFCI protection (at the breaker or at the outlet). Maybe even AFCI depending on whether that is code where you are. An electrician can do this.
Solution two is to not use the outlets at all for anything, or at least not for anything that has a ground connection.
Solution three, which really cannot be recommended is to replace the outlets with GFCI types. If you are determined to use the outlets for three-prong devices, then at least use GFCI outlets. This is better than using them as-is. Not recommended, but if you are going to ignore the best advice, this is kind of like fallback advice for those who don't listen.