Dayumn Phat, you sound like me, ie, I still have a Win 98 box too. I've got an old one that I built years ago that I still use as a Quake II game server and it still works well for that. It's not used on the internet though, just my LAN.
RE: XP? I've got multiple PCs and laptops that have that on them and I'll continue to use those until I run into something that I need to run and can't do with them.
I've got a couple of hard drives that have XP x64 on'em that have been run with no antivirus software for a few years now with no problems. Just have to be careful where I go with those though.
For "questionable" sites/surfing I use Ubuntu Linux as all 4 of my systems are multi boot using different hard drives for the different operating systems in the same case. I just choose the boot drive in BIOS at boot up. The desktop in my shop has 6 hard drives in it and each one is bootable.
That computer has XP, XP x64 (2), Vista, 7 and Ubuntu 12.04. Most of my time on that computer is spent on either Ubuntu or XP x64.
Why so many OSs in one box? Well, because I can for one. The other reason is I do some computer repair/maintenance for the locals here so it's nice to have one that is working OK when troubleshooting one that isn't. I have copied some files from mine and put them in one that had corrupt ones. In fact, did that on an XP box two weeks ago.
Ennywho, I'd bet that there will be LOTS of ppl still using XP well into the future especially if the antivirus ppl keep supporting it.