There is no "pure DOS" in Windows XP.
Just use the Windows interpreter and be done with it.
In any case, do this to enable the Creative Music System to get FM synthesis working in DOSBox (for whatever reason it's disabled by default):

In DOSBox:
Z:\> config -writeconfig default.conf

Then, open that file with a text editor.
Find the line
cms=false
and change it to
cms=true
Then save the file and restart DOSBox.
Now you should have sound in DOSBox.
You should also change the line
keepsmall=false
to
keepsmall=true

To use the mouse with DOSBox, you have to click on the DOSBox window. Note that this will steal your mouse from the OS and you'll need to use a key combination to allow the OS access again. (I don't know the correct combo so I just Alt+Tab 😀)

By "pure DOS" I didn`t mean any DOS modes under XP, but just DOS.

If I had only DOS and no Windows at all and I needed to run some game with mouse enabled, how that could be done?

Might not be able to. Do you have an NTFS or FAT32-formatted partition?

FAT32 ofcourse. I never use anything else - because I very often change my operational system from XP/W2k to W98.

Get 2DOSWIN. (It's in Deep Thought.) It includes everything you'll need, less sound card drivers.

Like I said the last time this came up...Why not install the Windows version? ...or just live with the DosBox emulation.