CBS, trying like the rest of the networks to figure out how to use the Internet advantageously, announced Monday that it will offer two episodes of Two and a Half Men and two episodes of How I Met Your Mother for free via the Yahoo! website. The webcasts are being "streamed" -- that is, they cannot be downloaded onto a PC or watched on portable video players. Moreover, they will only be available for viewing for one week. CBS execs said that the experiment was an effort to attract younger viewers who spend more time at PCs than older ones. One CBS exec told Daily Variety that this week was selected because many young people may have received personal computers for Christmas presents and are out of school for the holidays. Meanwhile NBC has made available for downloading from Apple's iTunes Music Store a free Saturday Night Live parody music video featuring Chris Parnell and Andy Samberg.