Whats up wazoman, it seems you're new here, next time try to post in the help section (most of the helping members are over there)
anyways, first you need to download MinVerChk (Minimum Version Checker)
This program will show you the base firmware of your PS3, the steps are:
1-Transfer the MinVerChk file to a USB flash drive, as if it were an upgrade (e.g. x:/PS3/UPDATE/PS3UPDAT.PUP)
2-Insert the USB flash drive into the PS3′s USB port.
3-Install the update from XMB (This will fail and display the base firmware)
if the system version is 3.55 or lower then yes you can downgrade
Mnverchk download: http://www.ps3news.com/forums/attach...chmentid=31151
& check this thread too: http://www.ps3news.com/forums/ps3-gu...hk-120995.html
Have a nice day.