Comparing contents of folders

I know that there is 3rd party software available to compare the contents of folders, but are there some features or utilities within Windows XP that does this? I frequently save information to my flash drive to take home and work on and then do not load back to my work PC. I do this erratically enough that I do not know what is where. So I would like to consolidate the two periodically. Currently I open the contents of a folder on my flash drive and copy it to the same folder on my work PC. But, I might forget to do this sometimes. Is there a better way to make sure that all files and/or changes on my flash drive are on my work PC?

Any suggestions? Thanks!