The NPD Group has released the list of the best-selling retail PC games for September 2006 in North America, with Electronic Arts' Glamour Life Stuff expansion pack for The Sims 2 debuting in the top spot, knocking popular MMORPG mainstay World of Warcraft into the second position. THQ's strategy title Company of Heroes was found as the third most purchased title on the chart, followed by The Sims 2, which fell from the second position last month into fourth. Also from THQ, the value priced Paws & Claws Pet Vet clawed its way up two spots to fifth for the week, followed by 2K Games' Civilization IV and newcomer Lego Star Wars II: The Original Trilogy from LucasArts. Another THQ release, Cars: Radiator Springs Adventures continued to build upon the popularity of the summer animated film by climbing up a single spot from last month into eighth position. Activision's Seaworld Adventure Parks Tycoon 2 debuted on the chart for the month in ninth, followed by a pair of expansions for EA's The Sims 2. The Open For Business expansion, which ranked fifth last month, fell five spots to tenth for the month, while Nightlife inched up one spot to the eleventh spot on the chart. Elsewhere on the monthly sales chart, LucasArts' Star Wars: Empire At War made its initial appearance in the fifteenth position, while 2K Games' Civilization IV: Warlords expansion fell dramatically from its fourth position ranking last month to eighteenth for September. The top twenty PC titles in North America for the month were rounded out by NCsoft's Guild Wars Factions, which likewise took a plummet from being the eighth most selling title in August.