Computer won't boot with my new cpu

Hi,
Today I tried upgrading my cpu from a Intel pentium E5300 to a Intel core 2 E7500, but after switching the cpus my desktop HP (Compaq 8000 Elite Base Model Small Form Factor PC) wouldn't boot and my gpu fan was very noisy. Then I tried the the procedures on a thread about booting problems, but nothing changed so I switched to my old cpu and everything seems to be working fine. I also tried to boot without my gpu and each ram on each slot so I don't think it's a psu problem. The only diference from one cpu to another seems to be (apart from the model and speed) the bus speed. I can't figure out the problem so any help is much appreciated. I'm 100% sure both cpus are working since I have tested them both on another computer just a few hours ago.
Links:
My desktop:
https://support.hp.com/us-en/product/hp-compaq-8000-elite-small-form-factor-pc/4065894/document/c01926347
E7500:
https://ark.intel.com/products/36503/Intel-Core2-Duo-Processor-E7500-3M-Cache-2_93-GHz-1066-MHz-FSB
E5300:
https://ark.intel.com/products/35300/Intel-Pentium-Processor-E5300-2M-Cache-2_60-GHz-800-MHz-FSB