[SeemosYantra]

Hello, and thanks in advance for taking your time reading. My main problem passed undetected until now, in which I tried playing a game which normally runs softly, but now was all choppy. Normally, when I have similar problems, I run a defrag, clean my temporals, and run a boot-time CHKDSK, after which things are normally back to good as new. Nevertheless, I found out I COULDN'T do it this time. Each time I programmed the boot-time CHKDSK, I rebooted and it would not even show the bluescreen, it would simply skip directly to WindowsXP. The problem is on my C drive, which is my system drive (hence the need for the boot CHKDSK). My computer is an AMD Phenom II X2 550 at 3.11GHz, with 3GB RAM, and 2 500GB hard disks. I'm running Windows XP Service Pack 3 with COMODO Internet Security as it's main firewall/antivirus. I didn't had any similar problem since it's very installation, more than a year ago.

The registry entry says:
BootExecute RE_MULTI_SZ autocheck autochk /p \??\C: autocheck autochk*

In advance, thanks for reading. Any help will be much appreciated.
PD: I already tried the fsutil command and it marks no errors. I can defrag normally my hardrive. I also tried the sfc /scannow command with no luck either. I installed the Recovery Console and managed to execute CHKDSK /r per suggestion of another person, and while it took eternity and said it had fixed some errors (it wasn't explicit at all), the main problem persists.