The MS Word regex seriously lacks functionality. If you absolutely need to stay in word (and can't find another editor that both has good regex support and retains MS Word markup), I found a possible workaround for you using the word regex:
1) Prefix every line with a character that you know does not appear in your text. Say "#". You would get:
2) Now do a "regex" search and replace with the following regex, which will find line 2 and 4 in this list:
(Read: everything that starts with "#", then has one or more characters (@) that are not "#", then has a digit, then 201 and then a digit again.)
3) AFter your search/replace, simply search/replace again and replace all the # with nothing.
You could probably also work with a VisualBasic macro for word, a quick Google shows that VB does have regex. Another Google shows that someone over at Stack Overflow already did something like this, apparently:
Another option would be to write a small script, like an AHK or AU3 script, that simulates keystrokes that do: 1. press down, 2. press home - shift+end - ctrl+c (copy line), 3. grab the line from the clipboard and test it against your regex, 4. press delete if line fits regex.
I am not 100% sure that above would work with all exotic possibilities for MS Word markup, but if it's just bold lines it should work.