INSPIRON 8600 BLANK SCREEN NO BOOT

I am trying to help my 70-year-old Mother in law use this computer to learn about computers and chat with some of her friends and relatives. Her sister gave her this computer this summer along with all the disks that came with it when it was new. She asked me to help her. She would like to get the Windows 10 upgrade if possible. So I used the disks to reinstall XP that this laptop came with. I upgraded it to service pack 3 in hopes of installing Window 7 Professional 32 bit/64 bit that I own. From here I would like to get her the free upgrade to Window 10. I have been working on this project for what seems like months now. Seem like just when I have found a resolution another obstacle occurs. My current problem is that now the power button turns on the power light solid but I get only a blank screen and so thought that I must have crashed the hard drive or needed to replace the memory. I ordered a new hard drive 40 gig I think that's what it came with. And also 2 one gig memory cards from amazon according to the specks in the Dell Inspiron 8600 manual and I installed these items as per manual. I also as per video took apart the power button assembly and reseated the orange strip and successfully put it back together again.  I still can turn on the power light and I have recently purchased a new battery and power supply that are both good. I try to run Windows 7 OS disk. and also XP OS disk neither one will boot. So far I am getting no display so I can’t get any bios or any kind of boot. If anyone has some useful advice for me I would be so glad. I hope it is just something that I have missed. I would like to at least give her this machine with Window 7 on it. Thanks.