Do a minimal install using the non-free cd for your architecture, when you get to tasksel deselect absolutely everything, then let it install, at reboot as root (you will only have the CLI) and using vi or something similar add the MATE repository
to your /etc/apt/sources.list
and
,then
then
then
Reboot, login install anything else you want like LibreOffice banshee, VLC, iceweasel, and have fun.

2.5 GHz is fast enough for almost anything. If it appears somehow too slow, try Xfce instead?

Support will end on April 8, 2014.

I was a little ahead I guess, but might as well be prepared for it.

so what if it stops? antivirus, firewalls, etc will still get updates. if he is using old computer, he probably doesn't need fancy apps that require latest directx or dotnet.

Usually when you get a message support will end it will end at that time, but when it is a release date it will be put offf if there are bugs. Can you atleast tell me when anybody has said that they will discontinue something that they haven't? Ms is moving to a new phase to keep selling, so in order to sell they will make certain products obsolete or unsupported & it doesn't have anything to do with hardware support, as a lot of the xp machines barely support vista which you can no longer purchase. Let alone try windows 7 on them & have to do a hardware hack. A lot of those xp machines will be unsecure unless they change to some light-wight linux OS. What happens if the operator does get an infection should they download all of the updates now & reinstall?
Why do we even tell people about their unsupported OS'es here at LQ why not let them go unsupported & suggest a firewall or ip-tables, in fact why update if you don't really need to?

Not true at all. Can you tell me of any AV that will install, and run on Windows98?

indeed, why update if there is no need? updates (at least the ones from Microsoft) could make system slower, they will fragment the old hdd and might require *more* RAM+CPU.

I don't know of av running on win98, but if he uses xp carefully, he might not even need one. there is always an option of offline scan in some other, modern, computer. or there are online av programs. he could create sha-2 sum of all (executable) files and send it online for scan, or compare it with known good values. firewall can be builtin home router, and I doubt it needs major updates for 'external' attacks.

after all, computer can be used offline, he didn't say internet was requirement :)
(he can use some linux livecd only for internet)

You mentioned AV after making a blanket statement so I asked you the obvious question. XP won't be supported by anyone much after MS withdraw from it. It simply wont be cost effective to make thigns like AVs, and other things you mention, work on so many systems.

And quite often those updates are critical for security.

I can already see you going 'but but but firewall and antivirus'...yeah, thats not going to help if (as it typically the case) some microsoft software is still connecting to the net.

You cannot measure speed from a pure MHz rating. P4 2.53s are not at all quick, they werent even that fast on release which was over 10 years ago.

Debian 7 GNOME/KDE will run pretty badly on that system. I wouldn't put MATE on a system for a new linux user. Doesnt sem that good an idea to use a fork of an ancient desktop that could be dropped at any time. Xfce and LXDE would work, but LXDE looks pretty horrid (IMO anyway). I dont know if Xfce would be any faster or slower than XP (should be faster than 2008 server though). If there is much in the way of video watching happening, and he's got a 6XXX nVidia card, linux could be slower overall than any (current) windwos version. Due to the 6XXX cards haivng some hardware video decoding features under windows, and none really with linux.

BTW, I ahve run debian 7 Xfce on a slower system (celeron 2.0Ghz, 512MB RAM, intel 845 video) and it ran fine. Hardly fast, but provided you didnt hit the system with too much at once it was OK.

and you know this simply because win98 doesn't have AV today?
I wouldn't be so sure. I think xp has more advantages over win98 than 7 over it.
if enough people cling to it, it will be cost effective to make AVs.

anyway linux is better solution in the long run.

True, sometimes the MHz rating can differ significantly. I have a similar experience, one Athlon XP clocked at ~2120 MHz and one Intel i5-2500K clocked at 4500 MHz, but the latter is 3-3.5 times faster than the XP instead of little more than 2 times (only using one CPU core). Boy is that thing fast. Eventually brought me back to Gentoo Linux.. :D

At least Xfce should do the trick on the OP's machine.

Regardless, if the OPs father isn't using the computer as it's too slow, why not try a live environment (http://live.debian.net/ has several DEs) and see if it runs sufficiently for the necessary tasks. True, you won't get an idea of HDD performance, but the other components can be tested and see if the desired DE (GNOME, KDE, XFCE, whatever) will run well enough to warrant further testing by installing to and running from the HDD.

Now, keep in mind the live environment may have to be run from a CD... P4 based mobos are a crap shoot as if they can or can not boot from USB, depending on the age. Maybe the OP will want to check if there is a BIOS update that allows booting from USB before continuing.

Booting from CD/DVD is not all that bad, just slow to get going. Once an app is loaded and running, however, it's fine.