on one of my PCs excel csv shows values in one column with Comma separation, please help

I have never explored this in great detail, but somewhere in Windows' Regional and Language settings is something like a "list separator" setting. Excel (and other programs) can use this setting to determine what character is used in delimited text files (like csv files). My guess is that one of your computers has a different character chosen for this system setting, and is no longer recognizing comma "," as the default delimited text file delimiter.