Im pretty new to UDK and i took a class to learn the basics of it made my own level and at the end of the class course they gave us the saves and told me to download udk for free so i did. Im not sure if it installed correctly, as i was installing it, it kept giving me a error about windows xp service pack 3. Even if the error still said the installation was going to stop it just kept going so i assumed it was nothing. I open up my level from my saves and open a save i do a little work then try to save, and it takes for ever and starts to say “program not responding” then it goes away then comes back. Was it because i dont have windows xp service pack 3 installed? i have a windows 7 64 bit really need help i enjoy using UDK and hopefully this can be fixed?
UE4 not UDK (free version of UE3), so which of 2 you mean? 
if UE3 then go to UDK forums as this anwserhub is for UE4:
https://forums.epicgames.com/forums/366-UDK
Hi supreme_dolan,
Yes, you do need service pack 3 for Windows if you wish to install UDK. Please visit the UDK forums at the link provided.