I am locked out of my computer

the data is vry insufficient..itz not clear as where the system is limiting u access..also the os platform u r using..

assuming, that u r having problem opening while logging in/off windows..
at the bootup n at "User Logon Welcome Screen" (user account management)..press Ctrl+Alt+Del at a time and only twice..it'll bring Classical Logon Window..now in the user name type 'Administrator' and hit enter..hope u'll b logged in..

reset the system using the reset button at the front panel..now turn off n unplug all..do the following:

1) see if the ram(s) is loose/faulty..open clean/remove carbon & or oxide formed on the teeth with an eraser n resit it..

2) unplug mains supply..pick open/remove the cmos battery..check (above +3v)..resit..

3) remove/clean dust neatly..dust is non-uniform in nature n may cause jam/short circuitry/excess resistace n many more..resulting an increase in heat..

4) open the CPU Heat-Sink with fan out of the socket..put some "Heat Sink Compound" (available in local electronics chip level spare market) between the cpu/processor and the CPU Heat Sink *** fan..resit/fit it tightly in position..

5) the smps itself may b defective/faulty..check the outputs of smps viz. 0v (black~ground); +12v (yellow); +5v (red, green~ps-on, violet~pg & grey~sb); -12v (blue); -5v(white); +3.3v(orange)..
the 'oscillator and error amplifier ic', or pwm switching regulator circuit..look for defective protector-transformer/resistance(esp 4.7k)/mosfet..

6) if itz not the smps, then it must b ur main/mother board..see with a debug card for mb error..may b short..look for defective capacitors(esp above 1000mfd)/mosfets..go through the mb's south bridge n the circuit lie around atx connector....

however, after logging in, do the following:
hv a licensed and UPDATED antivirus installed (i prefer avg/kaspersky, , without updation a full version antivirus is useless)..
download, install n run microsoft kb890830..http://www.microsoft.com/downloads/details.aspx?FamilyId=AD724AE0-E72D-4F54-9AB3-75B8EB148356&displaylang=en..
download n run Startup Control Panel..http://download.cnet.com/Startup-Control-Panel/3000-2094_4-10039330.html..'removeall the unnecessary startup items from here..(if u can't find what to remove,post me/us in ur comment with all the items listed in each n every tabs herein)..
remove all unnecessary software from add/remove programs..
download, install n run 'Advanced System Care Pro'..http://download.cnet.com/Advanced-SystemCare-Pro/3000-2086_4-10399324.html..
disable the following: a) 'Automatically Restart' right click on my computer->properties->advanced->startup n recovery->(uncheck on the) Automatically Restart; b)'Error Reporting 'right click on my computer->properties->advanced->error reporting->disable error reporting->(uncheck on the) 'but notify me when critical error occur'..
Increase the size of Virtual Memory, Initial: 1440; Maximum: 2880

always better to seek professional advice of ur system admin/vendor....