there could be loads of reasons why its doing it 
here is a few reasons 
1.when your starting the computer msn (etc) opens all at once and your trying to open the internet browser and the same time
answer: disable everything from loading up at startup (Except) anti virus firewall
2.you may need to run a disk clean up
answer: your computer may not have enough disk space left
3. you could have a viruses close everything and open anti viruses and do a scan
                
 danny
                
 October 2007