You can restore on a different computer that was never synced with the device, you will be able to unlock the device for use and remove the passcode, but your data will not be present.
You may have to force iPad into Recovery Mode
1. Disconnect the USB cable from the device, but leave the other end of the cable connected to your computer's USB port.
2. Turn off the device: Press and hold the Sleep/Wake button for a few seconds until the red slider appears, then slide the slider. Wait for the device to turn off.
3.While pressing and holding the Home button, reconnect the USB cable to the device. The device should turn on.
4. Continue holding the Home button until you see the "Connect to iTunes" screen. When this screen appears, release the Home button. iTunes should alert you that it has detected a device in recovery mode. Click OK, and then click Restore to restore the device.
Note: Data will be lost.
The only option is to wipe the device clean and restore it to factory settings. Hope you have a backup.
Follow the instructions in iOS: How to back up your data and set up your device as a new device http://support.apple.com/kb/HT4137 to restore the device to factory settings.
Once you have setup the device as a new one, you can then sync it back with your iTunes account and all your music, apps, contacts and any other content sync'ed with iTunes will be loaded on the device. Any content that is stored only on the device and not sync'ed with iTunes, like app logins or data, will be lost during this process. Be forewarned that this is a long process and can take a couple of hours or more to complete. This can be painful, but it is necessarily so to prevent users from working around the security settings. After the restore is complete, you can setup a new Restrictions passcode. Make a note of the passcode to avoid this situation in future.
Your backup will not do you any good at all. If you restore from a backup, you will simply be restoring the forgotten restorations passcode back onto the iPad! The only exception is if the backup was created before the passcode was set and you no longer have that computer. You will have to restore as new. After you restore as new, you can download your content again. See the link that Philly_Phan provided for that - and see the steps that Diavonex provided for restoring your iPad to factory settings.
But once again, do NOT backup the iPad, that will not do any good at all, and you will just be wasting your time.