Spica i5700: How to downgrade from froyo 2.2 to eclair 2.1 I have a Spica i5700 with Froyo version of 2.2.2. 

I want to downgrade it to Eclair 2.1, because I find the screen often produces erratic movements such as auto-input to my password even if I am not inputting anything. It also auto-scrolls, even if I am not scrolling it.
You'll need to use Odin.  This blog has a guide for how to flash 2.1.  To summarize you put your phone in Download mode, connect it to your PC, load the firmware into the appropriate field(s) in Odin and hit Start.  The site has a link to firmware but if it doesn't work try samfirmware.com.