Need Help Changing a Cell Into Multiple Rows

[shane01101]

So I have two columns of data that are over 10,000 rows which I need help splitting into more rows. I will give an example of my problem and desired Solution. Basically just trying to retain info from column A (which has only one value) for every cell I break up in Column B. Some of the values in column B have 20+ values seperated by commas and im stuck, please help!

Problem:

A------B
1000 200,205,207
1001 280
1008 200,207
1102 203,210

Desired Solution:

A------B
1000 200
1000 205
1000 207
1001 280
1008 200
1008 207
......