Stack multiple columns into one column... is there an easy way?

I have data I need to analyze with a Pivot Table, but I can't because there
are multiple columns. I have time series data, where the first column has the
item name, and the rest of the columns have weekly sales, one column per
week. However, I can't analyze it because I need the weekly data to be in a
single column (this is the only way I know how to analyze it and graph it).

Does anybody know if there is an easy way to stack this weekly information
into a single column, where the first column has the item name, second column
the date, and the third column the sales data? This will really help. Right
now it takes me 3 hours to re-arrange the data manually because there are
like 200 columns, each with 150 rows!

Thanks in advance.

I am having a hard time trying to picture what you are looking for.

Can you give a small example, say 5 rows by 5 columns of fake data so I can see the before and after desired effect?

Ok, for example:

STORE 8/1 8/7 8/14
Ralphs 500 250 300
Vons 150 740 200

And I need the data to be like this:
STORE SALES DATE
Ralphs 500 8/1
Vons 150 8/1
Ralphs 250 8/7
Vons 740 8/7
Ralphs 300 8/14
Vons 200 8/14

I hope this illustrates what I need.