The new SSD is likely slimmer than a hard drive, meaning you may need a spacer so that it connects to the system board. Example: [URL]    
Hi! I recently found my mom's old Inspiron 1545 in the attic and decided to make it my university laptop. I plan on installing Linux on it and switching the HDD to an SSD. However the system won't recognise the SSD (Intenso 2,5" TOP 128Gb) when I connect it to the original storage slot of the laptop. I have an optical drive to storage drive adapter for laptops and I tried the SSD with it and kept the HDD connected to the main storage socket and it worked. So I thought okay I just install the OS on the SSD and set the CD-ROM as the boot source in BIOS. Well that didn't work. The system won't boot that way. I tried updating the BIOS but that didn't help either. The only way I can use the laptop is when the HDD is connected to the storage slot and SSD is connected to the optical drive slot and the OS is installed on the HDD but that basically cancells the whole idea of buying an SSD to make the system faster. Could you help me identify the problem? Maybe there is something wrong with the SSD? Thank you!
SSD only works when connected to optical drive slot