mkwACT is really buggy with Windows XP service pack 2. Every time I would use it my computer would respond very sluggishly until I restarted. I tried to verify the md5 of a dvd recently and mkwACT couldn't even finish the job. It would freeze and then I'd have to restart. Trader's Little Helper is much better. I've had no problems with SHNs or verifying dvd md5s with Trader's Little Helper.