problem installing os x

hey everyone i came to this forum becuase i needed help with my imac. I bought it about two years ago and its been working perfectly fine and i have never had any problems with it until today. I was on safari browsing the web and the multicolored spinning dial continually showed up for long periods of time so i decided to restart the computer but it wouldn't so i manually turned it off from the back but when i turned it back on it got stuck on the white screen with the apple logo and the spinning dial. i called apple care and the guy told me to hold the shift key, hold the apple key option and the letters p r, hold the option key but nothing worked. He then told me to put in my os x installation cd and that i had to reinstall the os x but after running the installation i recieve a message saying there was an error installing the software try installation again. i have tried it about 4 times now and recieve the same message. Can anybody help me with this problem???

Boot up from the install dvd/cd and instead of an install, go to the Utilities menu and select Disk Utility. Do a repair disk and see what happens.
Do it a couple of times until you don't get any errors. Then try an install.
If you keep getting errors, it might be time for a new hard drive.