Mac extremely slow on startup - Snow Leopard 10.6.8
Hi, everybody. I have a Macbook Pro (mid 2010) with Snow Leopard that I've used without problems for years. Recently I installed Yosemite, but because of some hardware incompatibilities with my soundcard I went back to SL and everything went to ****. I did a clean install from my original SL 10.6.3 dvd, installed the updates to 10.6.8, but everything was running really slow. So I did it again, and again. Now the problem is that it takes a really long time to boot (like 15 minutes).
I follow all the steps at this link: http://www.macworld.co.uk/news/mac/steps-take-when-your-mac-wont-start-3423817/
In verbose mode (Step 4) I get the disk0s2 error a couple of times till it finally starts up. I runed the fsck (Step 5) till I get the "...seems to be ok" message, but next time I boot it's extremely slow again, and I get the same disk0s2 error if I run verbose again. Disk Utility says the hard drive is ok. I've repaired permits, reseted the NVRAM and the SMC, did a clean install again, but nothing seems to solve it, and I'm running out of ideas.
Any help would be great! Thanx in advance.
MacBook Pro, Mac OS X (10.6.8)