Dimension 4700,XP,PentiumR...Thinking Virus, then many problems...now no sign-on, password wanted-unknown..lastly keyboard lockout

-Virus warning, thought was malicious adware so ran adaware

-Got rid of adware, but computer background on desktop was stuck in one mode with virus warning box and would not change

-Changed computer to earlier date and the background problem fixed

-But computer was running slower, so ran Spybot and Housecall

-Not too many problems but fixed them.

-Suddenly though a few programs wouldn't work including my Sprint Sierra Wireless said No device found although it was in and working.

-Then when I restarted after the scans, windows opened up differently, now requesting a password, which I have never used or known.

-Tried a non-free password recovery program and burned the disc, but would not boot up with the disc.

-Tried options from the program owner, no results, got worse.

-Lastly, after many attempts all I get is a black screen with a request for the system password (unknown) and now it even locked the keyboard.

I have at least 3000 pictures, photos in there and programs with no discs and no XP program or backup, I am a single mom and no techie, I bought this used, not from Dell.

If anyone can help,  I do have the service order# and IP#, and realize the leap in faith due to hackers and dishonesty.

Please help me!!!

Thanks so much,

Mary Ann Locke