Looks like the E7400 won't even be electrically compatible, because the motherboard, even for socket 775, is on the old side. Looks like zero Wolfdale support and Conroe support only. Wolfdales weren't out in 2007. (pre-mid-2008 motherboard, by the looks of one of the screenshots) Conroe is 65 nm and Wolfdale is 45 nm. I would try the E6550, (if it's the Core 2 Duo E6550) as it realistically looks period correct with 2007 and possibly 2006 as well. (If you see a chip called the Pentium E6xxx, then it's a Wolfdale, and those likely have 2 MB of L2 or similar.)
"Working" vs. "being supported". Two entirely different things. As a rule of thumb, if the CPU has support for NX bit (DEP) and a few other newer CPU instructions, Win8 and later should install. I have an Intel Celeron machine without hardware DEP and Windows 7 is the highest it can get.
1.49GB of ram that machine must very slow i dont see what u can do with that unless u got SSD to compensate .
First at all: to be honest, the speed is quite fast for low power 13 years old computer, it's even faster as an Acer Aspire One D270 N2800 with 4GB of ram and WD Black Scorpio HDD 7200rpm, which also just has a 2 Core Atom CPU! Windows 10 Pro 1903 even works as fast as the Windows 7 Ultimate on that D270, with below the halve of the available RAM! In the meantime, I although tested the other 2 775 CPUs (E7400 + E6550)), and those will not work on that machine. The reason could be the FSB of 1066 E7400) and 1333 (E6550) while the MB is running at FSB 533 and/or 800! The Core2 Duo E4600, which works well, run on FSB 800! It would have been fine if the E7400 with 3MB Cach or the E6550 with 4MB Cache had worked, but they didn't! Max possible RAM would be 2GB (2 x 1GB) and I'll be looking for an extra 1GB RAM to get that machine working with 2GB. As that RAM is SODIMM DDR2, I'll be looking for one of the same specs I have, at now I've DDR3 and DDR4 but DDR2! The price for SSDs is still too high for 500GB-1TB in Thailand and not worth for that old machine. For the time being, I'll just use that machine for some 'bogus' work and to store some data, etc. which not on the safe side or really needed! It's just fun to play with such old machines! I although plan to install Terabyte BootIt BM and play with some other low power and older OSes too.
Windows 8.1 is faster for hard disk. Faster at all in my tests however I have never tested Windows 10 with SSD but with hard disk Win8.1 was better here. Small size SSDs usually have low prices.
I'm not surprised. I had Windows 10 installed on an ancient PC with Sempron CPU from the Athlon64 era and a 6600 card from Nvidia. Sadly the motherboard died a while ago when I tried to clean the dust so I threw it in the garbage, but I remember it worked almost normally. Also the Core 2 era was really great, I had a few of them, an E2180 that would OC to 3GHz, and an E7200 that would go to 3.3GHz or so quite easily. Really cheap, very good performance for that time.