Does that PC have an Athlon 64 processor by any chance?
I know that there is an issue with installing SP2 on some machines with an Athlon 64bit CPU inside.
MESH have been very active in looking at this problem, so you might want to search these forums first (as it has been discussed here) and then possibly ask MESH directly for advice.
Note - this is not a problem exclusive to MESH, it is directly related to AMD 64bit CPU's. Luckily (for you, possibly) MESH seem to be the most proactive in resolving this issue.