I have a dell vostro 1520 the number 9 display light is constantly on and if i type i it comes up 5 any advice

Attach to external monitor, if it works, there is a fuse that is blown near the video output cable. Not big enough for a novice to fix.
If not shown on external, it is a dead lcd, or bad solder ball issue. Quite common on those models.

Fuse details may be shown on my webblog. "Getting In Too Deep" Google it. Then search for Dell - it should come up in the list.

If BIOS password is enabled, only way to get rid of it is to perform BIOS reset. Has to be done by BIOS jumper, or some cases removing the CMOS battery.

Try to uninstall and reinstall the touchpad driver under device manager then restart the computer.

Copy and paste the following URL to your web browser:
http://support.dell.com/support/edocs/systems/vos1510/en/SM/html/trouble.htm#wp1092170
Here are the Diagnostic Light Codes During POST for the 1520.

First, please check that if your Dell Vostro 1520 battery and laptop connection place is clean, please clean them and test if it will get better.Else, you can find something useful in this article's last post: battery can't be detected by laptop

Most major manufacturers supply manuals online so if you were to log on to the manufacturer's web site, you may be pleasantly surprised as usually, if available, one is able to download, by model number, Customer Instruction Manuals, Dealer Network for spare part supplies as required.

The information is normally free of charge.

I hope this helps.

Might be:
- your power supply is dying
- corrupt boot files
- hard drive is dying.
Please list more symptoms

try this.
turn the pc on and hit ctrl+alt+delete (task manager)
if it comes up
click new task,
type in explorer.exe
and click next
it should work but not always
if it does immediately download and run Malwarebytes free version from www.malwarebytes.org.
see if you catch a registry problem
also if you know how when you save malwarebytes to desktop it will show up as MBAM.exe...rename it to winlogon.exe install, update, and run full scan.
Good luck
If this helps you resolve your problem, please
consider giving me a good rating and a quick
"thanks" or "good job".It will help me as well.
Thank you.

"my eyes becomes too weak?" (sic) With respect, you may need eye glasses?

open the case then locate the memory and make a clean all pin connectors of memory using a paper eraser..