IMac severe lag upon start up

Hey guys, I really need help,

I ws saving a movie fr YouTube on my mac in After Effects cs5,

But instead of saving it as a QuickTime movie file, I saved it as a PNG sequence, which is a picture fr every frame, there ws a few thousand frames, and I forgot to make a folder, so there is over a thousand picture files on my desktop,

It completely lagged out my mac fr a few hrs so I turned it off, when I switched it back on after about 5 seconds without even any icons popping up or anything it froze, so I thought maybe if I leave it on, it will un freeze, it didn't work, so now every times switch it on, it freezes after about 5 seconds,

I haven't been on it in a few days because of how bad, and frustrating it has been,

I would be extremely grateful if some one was able to help me get around this problem, I really need help.

It would be handier if you could contact me on Skype as I'm nt on these forums much, add mark.davidson19 on Skype, nd I will be on my iPad and if you want will show u fr yourself what it is like, however if you do not hav Skype, I will be looking back at this forum for the next few hours,

I would be extremely grateful if you can find away around this,

THANK YOU