I've yet to see any payoff to such in XP.
Can you find a web site that shows some benchmark (that's the payoff) on this?
I had an experience of corrupting registry (on my XP professional system) while compactifying registry by using Winrescue XP. For some reason the program failed while compactifying the registry and blue screen occurred. When I restarted the computer, booting was impossible because of registry corruption. I am wondering which program has safeguard against such failure, thereby safely defragmenting and compactifying registry?