Guess what happens in Vegas really does stay in Vegas. The bad buzz surrounding the much-publicized backstage turmoil on the set of ''CSI: Crime Scene Investigation'' has not affected viewership of TV's most popular drama, judging by this week's Nielsen ratings. Thursday's ''CSI'' rerun was the week's biggest draw, scoring 13.1 million viewers. It was one of eight top 10 shows that belonged to CBS, the week's most-watched network, with an average viewership of 7.9 million.
Reruns aside, ''The Amazing Race'' continues to be a huge hit for CBS; it finished fourth this week with an audience of 11.1 million. ''Big Brother'' also did well on Tuesday and Thursday, though Saturday's episode plunged to No. 58. Reality shows also paid off for Fox this week, with 9.2 million Paris and Nicole fans tuning in to ''The Simple Life'' (No. 11) and with the debut of ''Trading Spouses'' scoring 7.5 million viewers (No. 23). Still, the network finished fourth (5.1 million viewers), well behind NBC (6.6 million) and even ABC (5.7 million). UPN edged out the WB, 2.4 million to 2.2 million.