Sims 3 installation problems

hello, i'm having problems installing the sims 3 game. after entering the registration key, it starts installing and while it's installing a tab opens and it says : CRC Error: The file c:/program files/electronic arts/the sims 3/caches/sunset valley.objectCache doesn't match the file in setup's .cab file. The medium from which you are running the setup may be corruped; contact your software vendor.
and then there's the option: abort, retry, and ignore.
if i go for abort the whole thing goes over again, if i go for retry it continues installing but stops st the end and just blocks and if i go for ignore it asks me to insert the 2 cd and then blocks again etc.. what should i do?