In all honesty, that computer is so old that upgrading it is not worth it. The power supply connections will be different than modern components, the hard drive connections on the motherboard will be different, etc.
Have you considered a refurbished computer? Here is one from HP for $150 with Windows 7 Professional 64 bit, a Core 2 duo processor (much faster than your Pentium 4), 1 year warranty. As you probably know you can upgrade to Windows 10 for free if done by the end of July (or stay on Windows 7).
Here is the link:
https://www.neweggbusiness.com/Product/Product.aspx?Item=9SIV0MD3P55454&nm_mc=KNC-GoogleBizMKPL-PC&cm_mmc=KNC-GoogleBizMKPL-PC-_-pla-_-Desktop+PC-_-9SIV0MD3P55454&gclid=CjwKEAjw8Jy8BRCE0pOC9qzRhkMSJABC1pvJB5brZfILSzy8rh8n-LzaVSjIjuzHRIMIWrObMiMppRoCGzPw_wcB