These are actually multiple questions:
Q:My computer fan runs almost the whole time while I'm on my computer .
A: Vacuum that SOB! Vacuum the front first, then the back, then very VERY gently the inside parts.
Q: I have to turn off my computer at night because it will not stay in standby mode
A: Make sure it's not the mouse. in Device Manager (right click My Computer, Manage) go into the properties of Mouse and Keyboard and under power management, uncheck everything. Also go into the CMOS/BIOS/ETC (before Windows loads) and make sure power save settings are all set to S3, not S1.
Q: Also when I been on the net for awhile and my computer freezes up , I have to restart my computer and it only gets a blue screen with the little info on the bottom.
A: WRITE THAT LITTLE INFO DOWN!! If there's a file name, that may be the reason. It's probably a driver for something. See if you can't update the driver for whatever it's for.
Q: I then checked in the back to make sure everything in the back was plugged it right , I turned on the computer again and the WINDOW XP started up .
A: Congratulations, you solved that problem on your own! Always check the "dumb" stuff first, like loose connectors, stuck keys, etc.
Q: Also to add on when restarting the computer it just runs but the loading light in the front is not doing anything either .
A: Are you saying that when you turn the computer off, wait a little while, then turn it on, it works, but if you say "restart" it doesn't? That could mean it never finishes shutting down. Start, Run, MSConfig, OK, then under the STARTUP tab, uncheck one program, reboot. If it still does it, force it off and on, then uncheck another program. Repeat until it restarts properly. Also, they need to do way instain mother, but i digress.
Q: This has happen about four or five times within the last three month . What is wrong with my computer and what I need to do to solved this problem ?
A: Really, that's not terrible. If it's alittle over once per month, you've got a typical computer. More than that, I'd be alittle worried.
You should also ask yourself, did you install any programs or parts right before this started happening? is it something you can uninstall or do you need to keep it on your computer.
Hope this helps.