I would suggest that with a machine with a spec you have described you have no problems! Such a machine should be able to cope with all modern software except, possibly, the most complex games which will need a more sophisicated graphics card, a 64 it system and a quad core processor. You are not subjected to the curse of Vista and if your copy of XP has been updated to the extent you describe, it is vey unlikely not to be "Kosher". Somewhere on the machine's case you should find the Microsoft label bearing the unique serial number of your copy of XP with whch you can, should you want to, re-format your hard drive and then reinstall XP from any copy and use that serial number to validate it.
If you click on start, then hover over all programmes, then "accessories" then "accessibility" you will get to "magnifier". Click on this and hopefully, you will be able to change the settings which are causing the problem you describe.
P.P.