At least 20GB for C: where you install your operating system to, at least 25GB for D: where you install all of your 3rd party software to and the rest goes to E: where you are going to put all your custom files such as pictures, documents, downloaded files, video etc.
After you have installed XP, I recommend you to make a folder in E: named My Documents or whatever up to your preference and then change the path of My Documents to E:\My Document\. In case of system crash, you can easily format C: and reinstall all software if need to, without worrying to save your personal files.
After you have installed XP, I recommend you to make a folder in E: named My Documents or whatever up to your preference and then change the path of My Documents to E:\My Document\. In case of system crash, you can easily format C: and reinstall all software if need to, without worrying to save your personal files.