When it comes to buying inexpensive stocks, sometimes investors think that they can find bargains for just a few dollars a share. Sometimes they are right -- but other times these penny stocks can expose your portfolio to big risk and lose you a bundle in a hurry. Here are five popular stocks under $2 a share you should avoid like the plague.

Penny stock investing tends to be riskier than investing in large cap stocks, but that doesn't mean you have to settle for losers in your quest for big penny stocks that take off. Here are five penny stock losers to avoid:

Analyst upgrades:

• Wachovia upgraded shares of The Goldman Sachs Group Inc (NYSE: GS) to Outperform from Market Perform on expectations for greater pricing power given Goldman's position as the largest remaining independent securities firm.
• Keefe Bruyette upgraded Investment Technology Group Inc (NYSE: ITG) to Outperform from Market Perform as they believe the company will take market share with the reshaping of the large wire-house brokerage community. The company's target was raised to $37 from $33.
• Broadpoint raised Hoku Scientific Inc (NASDAQ: HOKU) to Buy from Neutral as they believe the contract with Tianwei New Energy reduces financing risk.
• ACE Ltd (NYSE: ACE) and The Travelers Companies Inc (NYSE: TRV) were upgraded to Buy from Neutral at Goldman.
• Axcelis Technologies Inc (NASDAQ: ACLS) was upgraded to Buy from Hold and Evergreen Solar Inc (NASDAQ: ESLR) was lifted to Hold from Sell at Citigroup.

Analyst downgrades:

MOST NOTEWORTHY: Cablevision Systems Corp (CVC), Nasdaq Stock Market Inc (NDAQ), Greenbrier Cos (GBX), Southern Copper Corp (PCU) and Hawaiian Holdings (HA) were today's noteworthy downgrades:

• Oppenheimer downgraded shares of Cablevision Systems Corp (NYSE: CVC) to Neutral from Outperform and does not expect a higher bid to emerge.

• Deutsche Bank downgraded Nasdaq Stock Market Inc (NASDAQ: NDAQ) to Hold from Buy, expecting only modest performance in 2007.

• Matrix cut Greenbrier Cos (NYSE: GBX) to Sell from Hold on the belief that slowing demand for double-stack and forest products rail cars is leading to slowing revenues.

• Credit Suisse downgraded Southern Copper (NYSE: PCU) to Underperform from Outperform based on valuation.

• Goldman cut Hawaiian Holdings (AMEX: HA) to Sell from Neutral based on weak fundamentals and increased liquidity concerns.

OTHER DOWNGRADES:

• Sterne Agee downgraded Blockbuster Inc (NYSE: BBI) to Hold from Buy.

• LoJack Corp (NASDAQ: LOJN) was downgraded to Hold from Buy at Needham.

• Axcelis Technologies, Inc (NASDAQ: ACLS) was downgraded to Sell from Hold at AG Edwards.

• CBL & Associates Properties, Inc (NYSE: CBL) was taken down to Sell from Hold at Citigroup.

• Morgan Stanley downgraded UBS AG (NYSE: UBS) to Underweight from Equal Weight.

Analyst summaries provided by TheFlyOnTheWall.com (subscription required).

Axcelis Technologies (NASDAQ:ACLS) designs, manufactures and services capital equipment for the semiconductor manufacturing industry. Its principle offerings include ion implantation systems, dry strip equipment, thermal processing systems, cleaning devices and curing systems. Most of the largest chip makers in the world are on its client list.

The firm pleased investors last week, when it guided Q4 EPS to 11-15 cents (12 cent consensus) and Q4 revenues to $115-$125 million ($121.2M consensus). The CEO remarked that orders for both the implant and dry strip products were high in Q4. She also noted that increasing momentum in sales of the new single wafer Optima HD implant system is bolstering the company's prospects for 2007. ACLS shares popped through stout moving average resistance on the news and then began formation of a bullish "flag" consolidation pattern. Stocks frequently exit a flag with a move in the same direction they were traveling when they entered it. In this case, that would be to the upside. Note that the 90-day moving average curve is currently supporting the flag.

Brokers recommend the issue with one "strong buy", four "buys", seven "holds" and two "sells". Analysts see a 15 percent annual average growth rate, through the next five years. The stock's Price to Sales ratio (1.56), Price to Book ratio (1.47), Price to Cash Flow ratio (15.04), Sales Growth rate (40.50%) and EPS Growth (-0.02 to 0.12 yr/yr) compare favorably with industry, sector and S&P 500 averages.

The stock is one of those used to calculate the S&P 600 SmallCap Index. Institutional investors hold about 94 percent of the outstanding shares. Over the past 52 weeks, ACLS has traded between $5.16 and $8.20. A stop-loss of $5.80 looks good here. Note that the firm is expected to report Q4 results on January 31st, after the closing bell.

Larry Schutts is a contributing editor for Theflyonthewall.com and the Vice-President of Stockwinners.com.