oh gawd. depends on who you're doin' business for. most my customers are small business owners as well as some of the cities credit unions, various city depts. and employees (not a bulk of 'em, but enough to keep up a good rep). theres nothin' shiattier than a disappointed customer thats missing data. even if its something stupid like they stored their data on the desktop in the "all users" folder, or they're too stupid to remember their password to their bank and they think its your fault you lost it, or they're too stupid to use bookmarks because they relied on their ie history you wiped..
IF ITS XP YOU HAVE TO REMEMBER TO BACK UP THE "ALL USERS" FOLDER. not everything hits the users profile folder. and they won't always tell you about the special business software they use that stores all its data in its own folder. you gotta scan the root, eyeball the program files folder by date as well as review the start menu for anything they won't tell you about.
working on a computer for someone is like an episode of "house". people lie. and they're stupid.
the thing i wonder about is whether my customers give a second thought to the porn i transfer for 'em (of the prostitute in their home), or the old user profile folders i dig out that they don't know they have thats got porn or other unwanted stuff they wouldn't have wanted the computer guy (or the rest of their family) to see.
i remember every customer complaint and the person that complained. that and i charge 95 an hour.