This is my first post guys so take it easy on my ;-)
I have been having the issue of disk 1 not being recognised on my old 360 for the last month after my slim threw a hissy fit and threw all it's toys out of the pram and, as it happens, all of my game saves from the last 6-7 years. Since then, I have had to revert back to my Phat that was hastily repaired and brought back in to service. That was great for Netflix and ALL of my other games that I have got on disk apart from GTA V.
After wandering around planet Google for what seems to be an eternity and getting sick and tired of everyone and his wife posting that Rockstar recomends not installing disk 2 blah, blah, blah.., Clearing the cache 3 times, rotating your xbox counter -clockwise 7 times on a full moon in the presence of a sacrificial virgin and other non sensical witch trickery, I landed on a possible fix.
If this has been covered ad-nausium on these forums, I appologise, but no end of hours has been wasted by me to get back to Los Santos to carry on the good fight.
The work around for this issue that worked for me was, instead of going straight ahead and install disk 1 onto the hdd from the dashboard, go ahead and put disk 2 into your console, select play game from the dashboard, and leave it until the game complains that you need to install disk 1 first, eject disk 2, insert disk 1, then leave it for ten minutes whilst it installs flawlesly, then it will tell you to swap to disk 2 and hey presto, back to kicking **** and taking names in Los Santos.
Now at this point, I should remind you that I found this resolution online and do not have the name of the poster. I just thought it may help the people that have this game but cannot install the first disk.
Anyway, thats that for now as I intend to buy a golf club in the very near future.