Many of you want to break into a windows system,either for accessing the files,or installing programs without the admin's knowledge.

If you just want to access files in the windows machine,just get a bootable linux cd. With it u can boot the machine, grab the necessary files in a removable usb flash drive,and shutdown the pc,without altering anything in the system,and without any admin/user password.currently my favourite live cd is knoppix. It supports maximum hardwares and also easy-to-use.knoppix can be obtained from the internet free-of-charge. Do a google search at the right side of the page. You can also use other live linux distros at your choice, and a few system rescue cds also does the job fine.
Above method works fine if you are dealing with a non encrypted windows file system,where simple access to files enable you to view their contents. But if the windows partition you'll break into uses an encrypted filesystem, you wont be able to view the files' contents. In that case you must login using passwords,and admin accounts are the best for this.you can use two methods for cracking windows admin pass-

1.If you have plenty of time,crack the system sitting in front of it. Use a superb tool named ophcrack. It is found in a live cd,at sourceforge.net. Load it into the cdrom drive,let it boot automatically,and select the windows partitions to crack.it will crack 99.99%passwords if they are under 15char length. Most windows passwords are much shorter than this.

2. If you are in a rush,e.g.while snooping on other peoples workplace computer,change your strategy a bit. Use the linux live cd i mentioned earlier,grab a file named password hash from the windows system,usually found in c:\windows\system32\config. Save the hash in a flash drive. Next,obtain a copy of rainbowcrack,and some rainbow tables.install it to a pc which is your own,and load the password hash from the target machine.let rainbowcrack run awhile,and your problem will be solved.

All the tools mentioned here are opensource,and can be obtained free of charge.