U.S. computer retail sales on Black Friday were slower than the same day a year ago, according to a new study.

Year-to-year growth for Black Friday 2006 for all PC unit sales amounted to 22.9 percent, slowing from the 36 percent growth seen in 2005, according to market research firm, Current Analysis. The slowdown figure includes computer desktop unit sales which were down 7.2 percent, the report found.

The portable computing category, however, continued its strong performance, with unit sales growing a robust 51.6 percent.

The strong growth in notebooks reflects the aggressive pricing strategies that manufacturers have undertaken to boost sales during the key holiday selling season, just ahead of the Vista launch, said Samir Bhavnani, Research Director at Current Analysis.

The week of Black Friday, the Friday following the Thanksgiving holiday, is traditionally one of the busiest shopping times of the year as holiday shoppers flock to retail outlets to take advantage of deep discounts.