You can use TAB on the keyboard to get to the button then press space bar  to click OK  ,OR just ignore the issue and wait for it to continue.   It will get past that point eventually with an unattended install.    Drive Mode should be set to ATA or Combination mode not RAID OR AHCI.
I am planning to pass on my old XP to a local charity, after wiping the memory i am re-installing Windows,all working fine until the following message received ;-   To improve the appearance Windows will automatically adjust your resolution,   An arrow is shown which has to be used to click OKAY,  up to this point the keyboard had been used, however when plugging in my mouse although it is live the arrow will not move.   I cannot progress until this problem is solved and the PC will be of no use to the charity.   iF ANYBODY CAN ASSIST I WOULD BE VERY PLEASED =============================================
Re-installing Windows XP