So you want to filter on .jpg files?
Could you start by filtering only .jpg
files in your hash lists first, e.g.
grep -E '\.[jJ][pP][eE]?[gG]$' winXPimage1.txt >only-jpeg1.txt
grep -E '\.[jJ][pP][eE]?[gG]$' winXPimage2.txt >only-jpeg2.txt
Then get your list of md5s on the first system:
cut -f 1 -d ' ' only-jpeg1.txt > only-jpeg1-md5only.txt
Finally attempt your inverted search?
grep -v -f only-jpeg1-md5only.txt only-jpeg2.txt
Update: had to edit because my first two example lines had -v
flags which I definitely didn't want. Well spotted by @Alex.