"win98 supported dos programs
it is very bad of win xp not to support dos programs"

XP does support DOS programs.
But no multitasking OS can allow tasks unfettered access to go writing willy-nilly to any old hardware address at will!!

The same applies to Linux, UNIX, and any other real multitasking OS for a general-purpose computer.

So, the kind of DOS programs that won't run under XP (or NT, or 2000 - and possibly not really 98) are where programmers have been too lazy to use the proper DOS/BIOS APIs, and have just hacked directly into hard-coded absolute addresses.
eg, my scanner driver is like it: it's hard-coded for LPT1: - so even if my PC has an LPT2: (or LPT3:) card fitted, there is no way I can use it. :-(
The driver developer was just too lazy to use the BIOS APIs to determine the available ports, and let me choose! :-(
It goes without saying, of course, that this scanner doesn't work on XP! :-(

So, if you want all the advantages of multitasking, peripheral support [1], fancy graphics, etc, etc, you just have to accept that no OS can reliably give you all this and allow you uncontrolled access to go poking about direct to the hardware!
On the other hand, if you feel that multitasking, peripheral support, fancy graphics, etc, are all a waste of time - just stick to DOS. Just think how fast it'll go on modern hardware!!!

[1] I remember the days of DOS when you needed a different printer driver for each program you used - so for just one printer, you'd need a driver for Word, a driver for your graphics program, a driver for your CAD program, a driver for... etc, etc.