Solution! I, just like you all, have found the same problem, when before, I could play and install the sims with no problems (save a few graphics hickups) and then, all of a sudden, it wouldn't recognise the disk! at all! But now, I have found the solution!! Hooray!! I run XP home and when I put a CD (or DVD) into the tray, a dialogue box pops up asking me which action I wish to take. These range from play DVD, through open CD writing window to Take No Action'. Whilst recording a CD recently, I chose 'open a CD writing window' and then clicked always take this action, which was a mistake. This prevented the Sims from reading the installation / game disks. I solved this by right clicking on the cd drive in windows explorer and choosing properties. I went to the 'Autplay' tab and then made sure that for each category of CD contents I had selected 'prompt me each time for an action'. After that Sims had no trouble reading the game disks. Hope this helps!! Jess