Windows xp home edition reinstall

Question

My brothers HP Pavillion a620n had Windows XP home edition pre installed.His system crashed and he asked me for help. Well he left and did not give me his backup disk.Used my original WindowsXP home edition disk to get his system to work. When I put in my disk the computer stated that his home edition was newer then mine.still used my home edition and got the computer to work Now have his disk and was wondering if his disk will be okay to use or do I have to reinstall my disk and have it do a format on the system before I use his disk?