Trouble with main disk on old macbook pro

I have recently been having some troubles with my computer. It is a a pretty old macbook pro from 2007 but has been working wonderfully apart from the CD drive that crashed a few years ago. I thought to heck with it and when will you ever need a cd drive? boy, did I have that wrong.
Recently the computer has gotten slower and slower and louder and louder and so I opened my disk utility and pressed Repair Disk to see if it would make any difference. The program responds by saying "the volume Macintosh HD has been found corrupt and needs to be repaired."
and
"This disk needs to be repaired. Start up your computer with another disk (such as your Mac OS X installation disc), and then use Disk Utility to repair this disk."

I doubt I still have my installation disc lying around and even if I did my cd drive would just reject it. I guess what my question is, if some kind soul would shed some enlightenment on the matter at hand, what it means that the disk is corrupted and when they say "such as you installation disc", does that mean that there are alternative ways of repairing the disk, and in this case, which?

grateful for any help
baltzar

You should never lose those original install disks....

However, all is not lost. Do this:

Boot the machine to single user mode: Hold down your command key and S key as soon as you hear the chime.

Next, type this in from the command line: /sbin/fsck -fy

Follow the prompts and let us know what it comes back and tells you. You may have to run this several times until all errors are cleared.

For the time being you could buy an external drive till you replace the drive in your laptop or get a new one.