Completely frozen after start up - overloaded

Hi guys, hope you can help.

I was busy backing everything up on an external hard drive. Afterwards when accessing the drive I couldn't seem to find all my photos. I then decided to copy my entire iPhoto library and drop it into the external hard drive icon on the desktop, BUT... I stupidly MISSED!! and dropped them onto my desktop. Over four thousand photos. Since then my computer will start up but the desktop is frozen. I can move my mouse around but it doesn't work. I can also hear ''clicking'' loading noise in the background. It's been like this for four days. I have followed all sorts of advice on this site regarding resetting and restarting computers, covering all sorts of different crashes but nothing works. Any ideas on what may help????? If I have to I will but don't really have the cash to send it in at the moment. It's an iMac 2007 chrome model. Sorry for the bad description but I'm not really a computer geek any help would be greatly appreciated

Cheers
Rich