Analysts' Upgrades, Downgrades: Nortel

Advance Auto Parts (AAP Quote) upgraded at Goldman Sachs to Buy from Neutral. See improving enterprise with market share opportunity, as well as low near-term expectations and a favorable macroeconomic backdrop for auto parts sector. Price target at $45.

AnnTaylor Stores (ANN Quote) upgraded at Piper Jaffray to Neutral from Sell. Fiscal 2009 EPS estimates introduced at $1.73. Introduces $23 price target.

Constellation Energy (CEG Quote) downgraded at Citigroup from Buy to Hold. $40 price target. Credit facility remains in effect, but strategic alternatives are just as likely to dilute current investors as result in a sale of the company.

Continental Resources (CLR Quote) upgraded at Merrill from Neutral to Buy. Company should outperform as it has a strong balance sheet and low cost structure.

Denbury Resources (DNR Quote) downgraded at Merrill from Buy to Neutral. $30 price target. Company focuses on tertiary projects that require substantial up-front investments, and could be hurt more by lower oil prices and a constrained credit market.

Holly (HOC Quote) upgraded at Goldman Sachs to Buy from Neutral based on potential upward revisions to near-term earnings for refiners. Also noted capital projects at Navajo and Woods Cross refineries. Price target at $45.

Kohl's (KSS Quote) downgraded at Citigroup from Buy to Hold. $52 price target. Valuation call, as the stock has outperformed its peers by 28 percentage points year-to-date. Fundamental outlook remains intact.

TCF Financial (TCB Quote) downgraded at Merrill Lynch to Underperform from Neutral. Cites elevated valuation and greater-than-anticipated credit strain in home equity, leasing and real estate. Lowered target price to $12 from $14.