Replacing first column value using VI

I have a Tab delimited file with first col value =I which i want to change to U.
Can I do this in VI? If so how?
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won' do what sollala wants :(
s/^I/U/ will only work if the I is the first character on the line, correct ??
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yes, could be improved like this:
 :%s/[ \t]*|/U/
(where \t is tab)
while  s/|/U/ changes also lines where | is not in the first column, like:
    sometext containug |, but not in first column
I see what you mean, I had based the construct on her original quesion idicating that the "I" was in the first tab delineated column, you're right about changing the I anywhere on the line.
oops, just saw that I should have writte I instead of |
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Unix OS

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