(Updated from 6:53 p.m. EST)

It was such a nice day on Wall Street for a change, and a typically quiet after-hours session, when

Apple

(AAPL) - Get Report

burst on the scene to ruin everyone's fun -- especially its own.

Casting a dark mood over the postclose session, Apple warned after the bell that its fourth-quarter results could be as much as 33% short of expectations due to a sales slowdown. The company added that the slowdown hit all geographical regions, its education market and its debut product, the Power Mac G4 Cube. The company will revise forecasts and growth targets for the year based on the disappointing sales.

Fourth-quarter earnings will likely be 30 cents to 33 cents a share, compared with the 45-cent

First Call/Thomson Financial

consensus forecast.

For the 33% shortfall investors shaved $24.93, or 46%, from Apple's share price, leaving the stock trading at a battered $29.06 on 1,393,426

Island

shares. And there is likely to be more where that came from in tomorrow's

Nasdaq trading.

Fair value for the

Nasdaq 100

futures is 3779.07, and they lately were trading at 3720. Also, the index shares tracking the Nasdaq 100

(QQQ) - Get Report

, another indicator, were trading 95 cents lower at $91.50.

Earlier Thursday, such heavies as

Bristol-Myers Squibb

(BMY) - Get Report

and

Procter & Gamble

(PG) - Get Report

said they would meet or beat expectations, soothing earnings concerns and starting a marketwide relief rally after days of malaise.

Intel

(INTC) - Get Report

popped 1.2% on earnings envy but sank 95 cents, or 2%, to $43.48 after Apple's bombshell.

This morning

TST Recommends

Dell

(DELL) - Get Report

made good in the confession corner. The boxmaker expected a strong fourth quarter to help the company reach its 30% revenue-growth goal for the year. It finished the session 3% higher but, alas, retreated $1.80, or 5%, to $31.63 tonight.

Optio Software

(OPTO)

was one of the few companies that escaped the carnage. It rose 31 cents, or 14%, to $2.43 tonight on bargain-hunting. The company provides businesses with the technical infrastructure needed for B2B transactions, and with the buzz and explosive competition in this sector you wouldn't expect this stock's yearlong price chart to resemble a precipitous roller coaster.

On Tuesday the firm scraped to a 52-week low of $1.96, and only by the mercy of blue-light shoppers refrained from sliding further. Yesterday the company wrapped up its International User Conference, Optio Exchange 2000, and saw its stock limp higher. Today it closed 3% higher and enjoyed a warm reception on Island ECN.

Cornerstone Internet Solutions

(CNRS)

was another example of fickle night trading. It started the session 9% higher and was lately off three pennies, or 9%, to 31 cents. The Internet services company helps clients improve business processes using Internet based technologies but perhaps it needs help first at home. Yesterday it hit a 52-week low of 37 cents, and it made a fresh low today.

Some investors already think the current market is a crapshoot, so gaming company

PDS Financial

(PDSF)

must feel at home. The Las Vegas-based firm deals in gaming equipment and announced right before the bell that it received regulator approval from the

Nevada Gaming Commission

for the marketing of a virtual blackjack game using digital playing cards. The cards are displayed on individual screens for each player and the dealer.

PDSF, which hit a 52-week high of $2.75 last Wednesday, this evening climbed 37 cents, or 17%, to $2.50.

Compaq

(CPQ)

named President and CEO Michael Capellas to the additional post of chairman. The news seemed to be overshadowed by Apple's troubles as Compaq lost $2.42 to $28.25 in sympathy, on almost 200,000 Instinet shares.

Research in Motion

(RIMM)

was moving forward late night. The Canadian wireless company beat the Street by a penny, posting a loss of 2 cents. The company said it spent more money on marketing, manufacturing and technology infrastructure, which then paid off a revenue jump driven by sales.

a

This information is provided by Instinet, a wholly owned subsidiary of Reuters (RTRSY) . For further information, please contact Instinet at www.instinet.com.

Island ECN, owned by Datek Online, offers trading, mainly in Nasdaq-listed stocks, from 7 a.m. to 8 p.m. EDT.

Confused?

TheStreet.com

explains how the rules change when the sun goes down in Investing Basics: Night Owl, a section devoted to after-hours trading.