I'm stuck on the gray screen on start up

Reinstalling Lion Without Erasing the Drive

Boot to the Recovery HD: Restart the computer and after the chime press and hold down the COMMAND and R keys until the menu screen appears. Alternatively, restart the computer and after the chime press and hold down the OPTION key until the boot manager screen appears. Select the Recovery HD and click on the downward pointing arrow button.

Repair the Hard Drive and Permissions: Upon startup select Disk Utility from the main menu. Repair the Hard Drive and Permissions as follows.

When the recovery menu appears select Disk Utility. After DU loads select your hard drive entry (mfgr.'s ID and drive size) from the the left side list. In the DU status area you will see an entry for the S.M.A.R.T. status of the hard drive. If it does not say "Verified" then the hard drive is failing or failed. (SMART status is not reported on external Firewire or USB drives.) If the drive is "Verified" then select your OS X volume from the list on the left (sub-entry below the drive entry,) click on the First Aid tab, then click on the Repair Disk button. If DU reports any errors that have been fixed, then re-run Repair Disk until no errors are reported. If no errors are reported click on the Repair Permissions button. Wait until the operation completes, then quit DU and return to the main menu.

Reinstall Lion: Select Reinstall Lion and click on the Continue button.

Note: You can also re-download the Lion installer by opening the App Store application. Hold down the OPTION key and click on the Purchases icon in the toolbar. You should now see an active Install button to the right of your Lion purchase entry. There are situations in which this will not work. For example, if you are already booted into the Lion you originally purchased with your Apple ID or if an instance of the Lion installer is located anywhere on your computer.

It appears you may have a bad Recovery HD partition. By any chance did you create a USB Recovery HD for emergency uses? If not, then I think you may have to first reinstall Snow Leopard then re-download and install Lion. Since you can boot into safe mode you can create a backup of your files because reinstalling Snow Leopard requires erasing the drive:

Downgrade Lion to Snow Leopard

1. Boot from your Snow Leopard Installer Disc. After the installer loads select your language and click on the Continue button. When the menu bar appears select Disk Utility from the Utilities menu.

2. After DU loads select your hard drive (this is the entry with the mfgr.'s ID and size) from the left side list. Note the SMART status of the drive in DU's status area. If it does not say "Verified" then the drive is failing or has failed and will need replacing. SMART info will not be reported on external drives. Otherwise, click on the Partition tab in the DU main window.

3. Under the Volume Scheme heading set the number of partitions from the drop down menu to one. Set the format type to Mac OS Extended (Journaled.) Click on the Options button, set the partition scheme to GUID then click on the OK button. Click on the Partition button and wait until the process has completed.

4. Quit DU and return to the installer. Install Snow Leopard.

This will erase the whole drive so be sure to backup your files if you don't have a backup already. If you have performed a TM backup using Lion be aware that you cannot restore from that backup in Snow Leopard (see below.) I suggest you make a separate backup using Carbon Copy Cloner 3.4.1.

If you have Snow Leopard Time Machine backups, do a full system restore per #14 in Time Machine - Frequently Asked Questions. If you have subsequent backups from Lion, you can restore newer items selectively, via the "Star Wars" display, per #15 there, but be careful; some Snow Leopard apps may not work with the Lion files.

What about the discs that originally came with the computer? Do you any other Macs that you can boot with the installer discs you have?

No. You need the installer disc to reinstall. Have you tried cleaning the DVDs as well as cleaning the optical drive? Can you insert an installer disc in the drive and see the files on the disc?

What you can try is one of the following:

• Get an 8 GB USB flash drive and clone the DVD to the flash drive using the Restore option of Disk Utility.
• Clone the DVD to a freshly erased external drive or free partition on an internal drive using the Restore option of Disk Utility.
• Make a duplicate of the DVD using the computer's optical drive(s).

Clone using Restore Option of Disk Utility

1. Open Disk Utility from the Utilities folder.
2. Select the destination volume from the left side list.
3. Click on the Restore tab in the DU main window.
4. Check the box labeled Erase destination.
5. Select the destination volume from the left side list and drag it to the Destination entry field.
6. Select the source volume from the left side list and drag it to the Source entry field.
7. Double-check you got it right, then click on the Restore button.

Destination means the external flash or other drive. Source means the installer DVD in the internal drive.

Duplicate a CD or DVD

1. Insert the DVD/CD;
2. Open Disk Utility, and select the DVD/CD from the left side list (select the DVD/CD icon on top);
3. From the DU File menu select New | Disk Image from Disk 1;
4. Choose to format the disk image as DVD/CD Master, name the disk image and click Save;
5. When the .cdr file is finished select it with mouse and press COMMAND-I to open the Get Info and check the box to lock the file;
6. Choose the .cdr file from the left side list, click Burn, and insert a new, blank DVD or CD.

I would consider cleaning the DVDs with a lint-free cloth and alcohol. Cleaning the optical drive is another matter, but you can purchase cleaning disc from places like Radio Shack, Best Buy, etc. You want something that will clean the laser lens and the r/w heads. Preferably use one that does not require using a cleaning liquid.

I assume you do not have another Mac you can use?

You can't. Has to be another Intel Mac or it cannot boot the installer DVD or install an Intel version of OS X.

If this is a Mac Pro 65 lb tower, you could remove the current Startup Drive and try starting with a different drive.

If this is a MacBook Pro laptop, ignore my outburst above.

Have you tried booting in Safe Mode (Shift key held down at Startup)?

It's a Mac Pro, I believe.

The reason I brought that up is there are some reports (rarely) where a corrupted drive may keep a Mac from doing the right things on startup. Removing (not just ignoring) the corrupted drive may allow starting over with a different drive.