You actually should buy a new hard drive. Do the data backup of your files, note what programs you have and see if they have any special settings you need to keep, then buy a new hard drive and intall a clean copy of Windows on it. Do not use the PC for long, the more you use it, the greater chance you have of the disk failing and losing all of your data.
I don't think it's a good idea to try to fix the errors on your existing disk as it will almost certainly fail again very soon, probably with no warning this time. At least now you have a chance to fix this with no data loss.
Another thing you may try to do is get a cloning software and clone your existing drive that is going bad, then restore that onto the new drive. Will be faster, but cloning software can fail when there are disk errors. To do that you need to have either a second drive installed or an external drive to save the clone image onto. Then you put in your new disk, run the cloning software again, and use the image you saved on that external drive to put it back onto the new drive. You should get your PC back good as new.