The writing (or not) to System32\Drivers\Etc may be because of the extra restrictions imposed by Vista and 7 - writing to any system or program files is restricted to Administrators. Unfortunately people either get fed up with agreeing to it all the time (Are you sure you with to allow this program to make system changes ?) that they turn the warnings off. Bad move.
XP Didn't have these restrictions until later Service Packs were installed.
If your PC is Windows and you suspect an issue another way to check is to run MSCONFIG from
1. A command prompt (Start, Programs or All Programs, Accessories)
2. The Run command in the Start Menu (if you have this enabled)
3. Task manager - right click on the task bar, select Task Manager, then File, Start New Task
MSConfig shows you which programs are scheduled to start with Windows in the Startup tab. You can clear out anything dodgy here - the programs stay in the list so you can restore anything you do by accident later. When you save changes it will ask you to restart to test the changes and it will come back up when you log in.
Another thing to check is in the registry (yes scary). Run Regedit and search for RunOnce. This section tells Windows to run the indicated programs once only on a restart and is meant to be used by installs which need a restart to unlock files. You will need to search for RunOnce repeatedly as there is one for each profile (and all profiles - i.e. user accounts).
A final one is to check for added toolbars and other add ins to your browsers. Each browser is different but they all have such options and lots of programs like to add little extras in there so that your browser goes to them when you search for whatever they do.
I'm surprised nobody has started the "why not use Linux" debate yet. I'm not starting it by the way, just saying (I use both so I'm an advocate of neither
)