*view File extensions:
To view the file extensions of a file
Go to control panel->folder options->view->
uncheck hide extensions for known file types
select the radio button show hidden files and folders
RAM
On the System Properties window, you'll see the type and speed of your processor (CPU) and the amount of RAM. Note that Windows always seems to report that you have slightly less memory than you actually have. For example, if Windows reports 496 MB of RAM, you actually have 512 MB. (Memory will always be installed in 64 MB increments.)

The more RAM you have, the better your computer will perform. I recommend you have a minimum 256 megabytes (MB) of RAM, but with 512 MB or even a gigabyte of RAM, you'll notice much better performance.

*SET Virtual memory:
control panel->right click on system goto properties->advanced->performance settings->advanced->Virtual memory->change->
Under Drive [Volume Label], click the drive that contains the paging file (virtual memory) settings that you want to change. In almost every case, this will be your C: drive.

Click to select the "System managed size" option, then click Set.

Click OK three times and restart your computer.
Virtual memory is a vast topic, am planning to discuss more about this sometime later

* System freezes:error message windows not responding
Reason: too many temporary files and startup programs.
slows down the machine by increasing CPU usage
Resolution:
start->all programs->accessories->system tools->disk cleanup
select all unwanted temporary file options and delete the same
secondly
start->run->type <msconfig>->startup->disable all unwanted startup programs

*Rename local admin password on the machine
control panel-> user accounts-> manage user accounts->reset password
NOTE:Only a user with admin privilege on the same machine can change this password .

* To view system information
start->run-> type msinfo32 in the run windows->ok