[SOLVED] Windows OS not reading my hard drive as installed and won't let me install windows 7

Jan 22, 2020
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So, im fairly new to computers. I know the basics, but as with everybody, I don't know everything. As the title says, i have a 250gb hard drive installed into my Dell optiplex 745 (blank) and tried to install windows 7. When I tried the drive was no where to be found not allowing me to install the OS. I have tried with several different hard drives, but the same thing keeps happening. Is it something to do with the motherboard? Just intrested.