I have an old PC but it is 32 bit currently running on windows 7, it's been a while I use it but I felt like just setting up another cold storage on it.
I will be changing the hard drive to a new one but I'm not sure which Linux distro and the self custody wallet that works on x86 Pcs or it doesn't matter?.
Old PCs are a very secure option if you set them up as cold storage. Since your PC is 32-bit and x86, it would be better to choose a lightweight Linux distro accordingly. I would use Debian with LXDE, or AntiX, both are lightweight and run very well on 32-bit.
Again, regarding wallets, there is a light version of Electrum that still runs well on 32-bit and is perfect for cold storage if kept completely offline. Just install it, write a seed phrase, and leave it without a net connection. You can also check out Armory if you want, a little heavy but great in terms of security. All in all, it is a really good idea to use old PCs in this way. Electronic waste is reduced and secure financial storage is created at the same time.