Intel Mac :: Error: This Disk Needs To Be Repaired

Since a week or 3 my Imac is bleeping whenever the harddisk is put to work. Before this it was impossible to make a time machine copy, it would hang at a certain point. I recently did a disk utility scan which could not be finished (aborted by the system) as it was saying (translated from Dutch):  

"Volume-information being checked Wrong amount of free blocks on this volume (Has to be 38684126 in stead of 38684119)The volume 'Macintosh HD' is damaged and need to be repaired.Error: this disk needs to be repaired. Restart system with another disk (like Mac OS X-installdisk) and use disk utility to repair this disk." 

So I put the installdisk 1 in, but the Imac spits it out, refuses to start up in harddisk repair mode or any other mode at all. It just spits it out and starts as usual. Install disk 2 it doesnt spit out, but I can only open a read me file. Like said, the Imac works fine, except that it is guided by literaly hundreds of beeps in high and low, short and long. I feel like being at a supermarket having my items scanned. That is what it sounds like. It is quite vocal but annoying and seem to multiply every day. In the beginning it only did at start up just a few beeps, then it got more, and now it beeps also in sleep mode.  

I cannot do a disk repair, also not with the latest OS X update (snowleopard, since Lion is not working on my 1GB drive). I do notice though that the difference in this error code is getting bigger, it used to be just one block difference, now it is 7.    

Also I took the memory modules out yesterday and put them back in, as I heard this can also help get rid of the beeps. It did not solve anything at all.I can't find anything on this problem on internet, because all beep related topics are about the error codes for the RAM drives. These are not the same sounds.  Another attempt was to install the cms program to avoid overheating fans. Also no improvement.

Info:
iMac, Mac OS X (10.6.8)