One of the problems you'll run into is that modern web browsers make use of more modern TLS / cryptographic standards for ensuring a secure connection to sites like this one. In some cases, sites will still allow using older (and insecure) standards, but in many cases they will not, and you'll thusly need to use a system (or web browser at least) that uses a modern TLS version.
A lot of browsers no longer support Windows XP because of the countless security issues with running an unsupported operating system, especially on the internet.
I would highly recommend not to connect to any WiFi or network connections, and to only use VERY trusted USB devices on the computer, to avoid getting infected with malware.
And hey, maybe that doesn't matter to you! That's totally fine! But an infected computer can also harm others on the internet, or your local network. So I would recommend using it to run older software, games, and other kinds of retro computing softwares (and even hardwares!). It can be a LOT of fun, but using the internet on these devices is not ideal.