How to top align all rows in table by keeping fixed width?

I am working on a LaTeX table and R, but I am facing some problems concerning column width and alignment.

cat("\\centering","\n")

cat("\\rowcolors{2}{burlywood1}{white}","\n")
cat("\\begin{tabular}{>{\\rule{0pt}{.5cm}}>{\\arraybackslash}m{2.25 cm}>{\\arraybackslash}m{2.25cm}c>{\\arraybackslash}m{7.5cm}c>{\\arraybackslash}m{2cm}c}","\n")
#cat("\\hline","\n")
cat("\\rowcolor{goldenpoppy} \\textbf{Col1} &\\textbf{Col2} &\\textbf{Col3} &\\textbf{Col4} &\\textbf{Col5}\\\\","\n")
cat("\\hline","\n")

In the above example Col1 is bottom aligned while others Col2, Col3, Col4 and Col5 are top aligned. Also how can I keep column width fixed?

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m{<len>}-columns have a fixed width of <len> and provides vertically centred alignment. That answers your question yet you're already using an m-column. So, perhaps you should rephrase your question...? –  Werner Jun 1 '12 at 4:22
Ok it seems to be fixed length but why fist column is Col1 it bottomaligned. –  manish Jun 1 '12 at 6:51