If you have experience installing Windows you don't have to buy a new PC with all the junk. I have purchased many refurbished PCs with no OS installed. I visit the PC vendor's website and make sure they have drivers for the target OS I plan to install on that model. I also check the seller's rep on Ebay/Amazon to ensure they accept returns in case of any problems. You get a custom OS tailored to your needs, no bloat. Even if you purchase one with a pre-installed OS you're better off wiping it and installing the OS yourself. A while back I purchased a Thinkpad that came with the original Windows 7 OEM install chock full of bloat/trial versions of Office, AV etc. It has 4 GB RAM but it was so slow even after un-installing all the bloat. I hated the fact that the Thinkpad utilities would auto-update, sometimes momentarily freezing the PC in the process. Grrrrr.
I did a system restore so it would revert to factory settings, imaged the whole hard drive (I did this in case I ever want to sell this unit I could restore it to out of box experience). Downloaded all drivers from Lenovo, installed Windows 7 Ultimate x64, installed all drivers and the only Thinkpad utility I found useful, the battery manager. The performance was night and day, the laptop was more responsive, no more freezes, no more auto-updates. Worth the effort.
As you mentioned that your PC is showing its age purchasing a replacement would be prudent before it completely gives up the ghost. Depending on your software needs you can stay with XP, try a newer Windows version or even dual-boot. Just make sure the PC you plan to purchase has drivers available for download from the vendor's website. You can always ask us if you have any questions on what model to purchase/recommend.
FYI XP browsers MyPal, Serpent and 360 Chrome all work perfectly in Windows 7 x64 and Windows 10 x64.