ApusDot

That PC has a B75 Chipset and support these 1155 CPUs:
Intel 3rd generation core i7 processors:
Intel Core i7-3770 processor:
Intel 3rd generation core i5 processors:
Intel Core i5-3570 processor
Intel Core i5-3470 processor
Intel 2nd generation core i3 processors:
Intel Core i3-2130 processor
Intel Core i3-2120 processor
Intel Pentium processors:
Intel PentiumG870 processor
Intel PentiumG860 processor
Intel PentiumG640 processor
Intel Celeron processors:
Intel Celeron G550 processor
Intel Celeron G540 processor
Intel Celeron G460 processor
https://support.hp.com/ro-en/document/c03387773
 
B75 chipset only supports Gen 2 (iX - 2XXX) or gen 3 (iX-3XXX) cpus.
So the highest it can support is the i7-3770 (listed above) or you can find list of compatible cpu here:
https://ark.intel.com/content/www/us/en/ark/products/64030/intel-b75-express-chipset.html
 
Now for the 4th gen, you need an 8th generation chipset (x8x)
https://ark.intel.com/content/www/us/en/ark/products/80806/intel-core-i7-4790-processor-8m-cache-up-to-4-00-ghz.html
So even-though it has the same socket 1155, the i7  4790 cannot run in your PC.
 
For the socket 775 mentioned in the manual, i guess it's an outdated information (copy paste galore), companies as big as HP can make mistakes sometimes.

Well the first mistake was buying an alienware laptop.

Did you run various spyware software? Sometimes just one program doesn't detect the trojan horses. You might have gotten more than just one and you only got to remove one of them. Try at least 3 different anti-spyware software, boot in safe mode, etc.

Did you run various spyware software? Sometimes just one program doesn't detect the trojan horses. You might have gotten more than just one and you only got to remove one of them. Try at least 3 different anti-spyware software, boot in safe mode, etc.