If you liked DOS, you will love Linux. Check around there are flavors other than Ubutu. Suse, Red Hat, etc. Nothing like the joy of a black screen and a blinking cursor waiting for you to guess what string to type. Not as bad as the MS blue screen of death, but amazingly close sometimes.
There are really several really annoying aspects to MS's decision to terminate XP support. Maybe a silver lining somewhere down the road like there was for those who did and still do hang out in the Win 98 world if MS releases the XP source code.
I really hated doing the switch to XP from 98. Hung in there and ignored Windows ME. But finally went XP just in time for SP2. Years later I am still on XP. Got my machine tweaked perfectly. Spouses machine runs Vista. Four years ago I bought 7. Can't tell you how sad I am to learn this useless 7 CD won't install on an original XP machine. I need new video cards and all that. MS advise, buy a new machine (and maybe 8 too). Pfui to that.
If you are running XP and it isn't running right and it isn't about not enough RAM I truly like Reimage Repair. Biggest issue I would see with doing that would be getting the no longer available from MS security updates into the machine after the Reimage Repair. I'd talk voice to one of their support people first before doing that. Pretty sure they probably worked out a solution by now. My suspicion is you have services running that you don't need, or a registry issue, or some hidden malware somewhere. AVG, SuperAntiSpyware, JV16, etc may help you find the problem. In the meanwhile go into Start - Accessories - System Tools - System Information - Tools - File Signature Verification Utility. Insert the original XP installation disk into your CD reader. Close the screen that comes up. Now run the System File Verification Program. Could be some of your system files picked up a lil corruption over the last decade. SVF will catch and replace them with originals from your CD. You can also do the same thing with a freeware program called Dial a Fix available from http://wiki.lunarsoft.net/wiki/Dial-a-fix
but only for XP or 98. Use the tools feature of dial a fix and purge the sfc files, then run the checker. Should take about 20 minutes. Then reboot.
I've got got SUSE hidden on this hard drive as an alternate boot in case of MS problems, but have to acknowledge I have my XP so nicely tuned that it's been at least 6 years since I needed it.
Biggest problem I had with Linux was many of my plug and play peripherals (including my modems(!?!)) wouldn't run with it. Check that issue out before installing. Nothing worse than having a working machine that can't go on-line.
I am going to hang XP at least until MS releases their Win 9. I have played with 7 and 8.1 machines and I am not impressed.