I'm using Snow Leo with iMac, and it's continuously getting slower and slower to startup. It's 35 sec (without weird HDD) at fresh install or after clearing PRAM. After 3 days now it's 50-60 sec. Last time before I've found out the PRAM trick, it was 90-120 sec.
Also there is a weird HDD scrawling at startup I don't know what. The 1st time refers to the desktop showing up with the menus, and the 2nd time is the actual startup finish, when the HDD stops scrawling, and finally I can open a google page.
Also when I clear PRAM, I lose nothing, but the startup volume, which is also gets corrected by the OsX at 1st start.
So can I have the PRAM or any special part of it (I'll just test if that helps) automatically cleared at shutdown (or startup)? It would be even better to clear it once in every 1-2 days, but if it's a script, I can modify it myself.

What do you mean by "a weird HDD scrawling at startup "? After you boot up and log in, go to spotlight and search for disk utility. Select Macintosh HD on the left and click on verify disk. You might also want to install Onyx to clear your cache and other useless items.

I need to know some of your specs

1) How old is your mac and what is your current version?
2) What is your ram?

Important Notes: Clearing the PRAM does not always help and could even harm your mac. Slow startup could be a sign that your hard disk is going to crash or fail soon.

commented: Good questions & advice +5