Most likely your boot drive has failed, or you have some other hardware fault. If you care about the last three days' worth of data, you should try to back up, if possible, before you do anything else. Don't overwrite any previous backup, because the files may be corrupt.
There are several ways to back up a Mac that is unable to fully boot. You need an external hard drive to hold the backup data.
1. Boot from your recovery partition (10.7 or later), a local Time Machine backup volume (10.7.2 or later), or your installation disc (10.6.8 or earlier.) Launch Disk Utility and follow the instructions in the support article linked below, under “Instructions for backing up to an external hard disk via Disk Utility.”
2. If you have a working Mac, and both it and the non-working Mac have FireWire ports, boot the non-working Mac in target disk mode by holding down the key combination command-T at the startup chime. Connect the two Macs with a FireWire cable. The internal drive of the machine running in target mode will mount as an external drive on the other machine. Copy the data to another drive.
3. If the internal drive of the non-working Mac is user-replaceable, remove it and mount it in an external enclosure or drive dock. Use another Mac to copy the data.
...the spinning gear under the apple sign. I then tried a safe start and the apple sign changed to a No Entry sign above the spinning gear.
Cant' fix the drive.
You have Lion, hold command and r keys and reboot into Recovery HD partition and use Disk Utiltiy to repair the drive or install Lion onto a external drive
If it's not seen on the left, it's likely dead, or the cable to it or the Mac, hard to determine until they pull it out and put it into a adapter to read it.
Review your data recovery options here