I used this Linux(?) program to erase the login password on Win7, Win8, Win10 ok - it takes a couple of minutes. If you want to use a USB stick (instead of a CD) use 'Rufus' to burn the iso image 'trinity-rescue-kit.3.4-build-372.iso' Rename the usb stick: 'TRK_3-4' it will allow the setup find the TRK file on the usb when booting. Boot using the cd or usb stick (from the boot option screen, f8,f12, whatever) At the Windows login screen 'Re-Start' the problem PC using the power options lower right of the screen - don't 'Shut down' as some versions of Windows 'hibernate' on shut down which prevents the Windows volume from being mounted by Linux. If successful, Windows will boot to your Desktop. Info: http://www.ricksdailytips.com/trinity-rescue-kit/ Author (sometimes site is down): http://trinityhome.org/ Can download the iso here: http://www.majorgeeks.com/files/details/trinity_rescue_kit.html
Hirens Boot CD would most probably be the better known,also contains a bootable version of xp. There's also another utilities disc that gets mentioned but i can't recall it's name at the mo edit: Yeah attar it'll be linux .
Can't remember if there was another admin acc as that's what the password was for (an admin acc i used as the guest was turned off) there was an admin acc that sp2 created however i hid it.Most probably tried safe mode mind you it was quite a few years ago,tho i do normally try the basics first i.e web search for things to try etc