Updating your snow leopard kernel is important. It's due to apple update is very fast. Many softwares minimum system requirement is now 10.6.4. If you not update you will not able to use the software. If you use same laptop as me, you will have no problem update, however you need follow step-by-step instruction.
It's important to delete NVEnabler.kext first. It will cause boot hang.
First, update from 10.6.2 to 10.6.4. Update can be obtain from apple website by just google it. Install 10.6.4 update. After install don't update yet. You will need to replace the SleepEnabler.kext. If not you will not able to boot. Download sleepenabler.kext by google "SleepEnabler 10.6.5". Replace SleepEnabler.kext at S/L/E. You need to use kext utilites after replace kext at E/E (Extra, Extensions) or S/L/E (System, Library, Extensions), because you need to repair permission for it. If you not using kext utilites, the new kext may not be able to used, and will cause kernel panic (BSOD) when boot. After that, go to repair disc permission at Application, Utilities, disk utilities. For every update you need to repair disc permission, if not you will get kernel panic. In fact, you need to repair disc permission often so your mac will function at top performance. Then restart.
You should be able to restart if you follow my procedure. Continue with above procedure for 10.6.5 update, except change sleepenabler.kext because the sleepenabler.kext above support 10.6.5. Use kext utilites and repair disc permission after update, then restart.
Note: Don't direct update from 10.6.2 to 10.6.7, or skipping any other update. I don't know why, but when I do that, I won't be able to boot.
Then, do the same for 10.6.6 update. Google "SleepEnabler 10.6.6" and replace it after update, use kext utilities then repair disc permission. Then restart. For 10.6.7 do the same. You should be able to boot successfully everytime, except the repair disc permission time will took longer.
I not yet update to 10.6.8 because I read that 10.6.8 change a lot and will most probably cause kp (Kernel Panic). 10.6.7 is already sufficient for most of the software system requirement, so I would not take the risk.