Need help Uploading a program onto my arduino!

My computer is currently running Windows Seven.
I recieved my arduino Duemilanove w. ATmega328 yesterday.
Last night I uploaded a program on to it and it worked great! But thismorning I tryed to upload a different program and I got this error message.

avrdude: Version 5.4-arduino, compiled on Oct 11 2007 at 19:12:32
Copyright (c) 2000-2005 Brian Dean, http://www.bdmicro.com/

System wide configuration file is "C:\Users\Spencer\Downloads\arduino-0022\arduino-0022\hardware/tools/avr/etc/avrdude.conf"

Using Port : \.\COM3
Using Programmer : stk500v1
Overriding Baud Rate : 57600
avrdude: ser_open(): setting dtr
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Recv:
avrdude: stk500_getsync(): not in sync: resp=0x00
avrdude: Send: Q [51] [20]
avrdude: Recv:
avrdude: stk500_disable(): protocol error, expect=0x14, resp=0x51

avrdude done. Thank you.

Please help thank you very much!

May we assume that you've parsed the troubleshooting guide already?

One further hint is in my signature.