Mac Os update, desktop error

[swainclubber]

i just downloaded and installed an update, i was on 10.5.7 and now when it switches on the desktop looks like big blue and black boxes.is there any way to revert back by pressing any keys etc (i cant access the dock etc)

many thanks in advance

ben

 

[swainclubber]

I also think a prologic update was done too if that helps. I'm new to mac so I dont know any proceedures