Microsoft Send Error Report

I have a Windows XP machine and no matter what I do I when I crank the machine up I get a message that the program has encountered a problem and needs to be shut down. I have recently added memory to the machine but that is the only thing that has changed. The only thing that I have been able to run with success is a defrag. The problems I run into are running Internet Explorer, Windows Media Player, and even doing a Virus Scan with Mcafee. They all run for a few minutes and then Microsoft’s Send Error Report window comes up and tells me the system has encountered a problem and needs to be shut down. When I choose to get more information it does not tell me much. The event viewer tells me that the application has hung due to a bad fault bucket. Could this be bad memory?