A Celeron has only one thread and even though bitcoin core's block verification is single-threaded it is guaranteed to be constantly at 100% CPU until it ends.
Celerons also have the unfortunate property of having a lower clock speed than almost every other processor, and that makes the verification much slower.
You can verify whether the CPU is the bottleneck by opening Task Manager and go to the Performance tab, then check the CPU graph and see if it's always full, and during that time the Network graph should be empty, or minimal.
Your disk should not be the problem unless the disk usage graph is full.
If however your RAM graph is almost full that means you are out of memory and Windows is moving around bitcoin core's dbcache around swap space. This is an extremely slow operation which slows down the program and ultimately the whole computer much more than a bad disk or cpu can.
No that is a 4 core 4 thread CPU
https://ark.intel.com/content/www/us/en/ark/products/78867/intel-celeron-processor-j1900-2m-cache-up-to-2-42-ghz.htmlAnd it's a 2 ghz going up 2.4 burst.
In the end the RAM & drive are going to be the limiting issue.
At 4GB you can increase the dbcache a bit depending on what else the system is doing.
The other issue tends to be lower end systems
in general tend to have other low end compmentes in addition to the CPU. Slower RAM, slower HD with less cache.
Less optimization options in the BIOS, etc.
-Dave