Merge Cell Wizard is an add-on that can do it but it's not free. I think the easiest way is to copy the cells into notepad. Wrap each line in notepad with quotes then copy back to excel. If you have ultraedit, then just go to search/replace all, turn regex on and replace ^p with "^p". Cells copied into a text editor will be delimited by a tab - so another way to merge cells is to get rid of the tabs then copy back into excel.
Insert a blank column in the spreadsheet and in the first row add a formula to concatenate the two columns you want. For example in Cell C1 add: =A1&B1 Then drag the formula down the column to apply it to all the rows you want.