Yes. It works on XP home and pro.
If you select 640 x 480 you get a file size around 50kb.
This is fine for viewing on your screen, not very good for printing, but you
can get a 6 x 4 out of it.
I prefer image resizer because you can select multiple files in a folder,
right click, click on resize, select the size and the resized files are
automatically added in your folder.
If the intent is printing, I would simply experiment with one file, resizing
it using each size available on the menu, and then print each resized file.
You would then be able to judge what is "good enough" for you.
If you use irfanview, resizing is not a batch option for this particular
function. You need to resize each file. You need to open the file, go to
Image and then resize. Select the size you want and then Save as and then
add something like resized to the file name. You also have to make sure
about the file type when Save as, irfanview may default to jp2 instead of
jpg, so you have to change this. The advantage is a better quality resizing
for printing, but you pay a price. The 640 x 480 file size will be around
250 kb.