Inspiron 5558 laptop verticle & horizontal lines

Sounds like you have a system board that's failing.  That's likely not worth the cost of repair on a  7-year old system -- start shopping for a replacement notebook.

Thank you, I have laptops older than this Dell also Dell laptops which are fine I don't get it.

It is most likely a faulty GPU -- not unexpected, given that the system has exceeded its design life by a factor of two.  Just as you've had systems last much longer, there are plenty that have failed long before now -- the laws of statistics rule.

ejn63 you obviously don't have a clue about this problem. I called into a local phone repair shop who instantly told me that the problem is screen only. I watched several YouTube videos which also advised that it was a screen issue. One advised to connect to a monitor or as I did my TV & the reproduction has no lines which tells me that it is screen & not a system board. Over the years with Dell laptops I have had several issues & not "1" has ever been resolved by dell support amazing when you think that we rely on support for help.

If so, then replace the screen and you're set.  

I'd cast a very skeptical eye toward anyone definitively troubleshooting and telling you that based on your description, though.  It is very possible (common, actually) for a failing GPU to work fine externally but not with the internal screen.  The chip is used to drive the internal screen most of the time, so that part of it very commonly fails sooner than the part connected externally.

Whether you choose to follow your own agenda or listen to others, the cause is almost certainly a bad GPU - not a bad screen, but the path forward is yours to choose.  Best wishes on a resolution.

It's clear your mind is made up - so go ahead and replace the screen.

Before dismissing advice, at least read it -- I said nothing about the CPU.  I mentioned the GPU being the faulty part.

Yes, initially the are pink horizontal covering around 50% of the screen then they change to vertical black, white & grey. You can still see the login screen faintly behind this.

So if you insist that this is definitely a CPU problem & not a screen please explain how it works by HDMI connected to a  a monitor?  I find that very interesting? Common sense tells you that it cannot work perfectly if it's a CPU problem.

Welcome to the Dell Community @lesallen45 

A picture with the lines displayed would be helpful???

When flexing the display do the lines change at all???

Best regards,

U2

@lesallen45 

Cold solder joints on the display.

The display will need to be replaced.

Regards,

U2

When you refer to the display are you meaning the screen?

My advice on a system of this age would be to replace it rather than replacing either the screen or the system board -- any system that's about 7 years old has exceeded its design life by a factor of two, and whichever you replace first, if you then wind up having to replace the other, you will have put more than $200 into a system that's not worth half that on the resale market.  It's your money;  proceed however you wish.

@lesallen45 

Yes, just the display screen.

Remove the LCD bezel using your finger nails.

https://www.dell.com/support/manuals/en-us/inspiron-15-5558-laptop/ins15_5558_sm/procedure?guid=guid-7d2f7688-78d5-42c1-a5e4-3c5f4d539e26&lang=en-us

Then remove the screws so you can see the Dell Part Number or the manufacturer Part number of the LCD on the label. 

Post the part number needed.

Regards,

U2