import re
s='''1.29.7D59 ; This field should not be edited
SE5C620.86B.00.01 ; This field should not be edited
I/O Sensitive ;Options: Balanced=00: I/O Sensitive=02
POR - Reg. Value:0x1F ;Options: 0.0%=00: 0.1%=01'''
print(re.findall(r'^[^;]*[^\s;]', s, re.M))
aW1wb3J0IHJlCnM9JycnMS4yOS43RDU5ICAgICAgICAgICAgICAgICAgICAgICA7IFRoaXMgZmllbGQgc2hvdWxkIG5vdCBiZSBlZGl0ZWQKU0U1QzYyMC44NkIuMDAuMDEgICA7IFRoaXMgZmllbGQgc2hvdWxkIG5vdCBiZSBlZGl0ZWQKSS9PIFNlbnNpdGl2ZSAgICAgICAgICAgICAgIDtPcHRpb25zOiBCYWxhbmNlZD0wMDogSS9PIFNlbnNpdGl2ZT0wMgpQT1IgLSBSZWcuIFZhbHVlOjB4MUYgICAgICAgICAgICAgICAgIDtPcHRpb25zOiAwLjAlPTAwOiAwLjElPTAxJycnCnByaW50KHJlLmZpbmRhbGwocideW147XSpbXlxzO10nLCBzLCByZS5NKSk=