I was assuming he still has control of peeing, so unless he decides he wants to go 24/7 I highly urge him to still use the restroom and wear a more discreet diapers.
Both are lower quality diapers meant to be changed like every 2-3 hours and depends on the amount of your flooding, but at most will take a single flood.
The biggest problem I find when an old computer starts running slow is that they have newer applications or these days web apps that require higher specifications.