I believe everything. OP's new computer have 4GB RAM and 7200 rpm hdd. Windows 10 OS consume more or near 2GB RAM so that left OP not enough to run browser and basic applications. When OP's computer run out of RAM, Windows will switch to OP's 7200rpm HDD for virtual ram or pagefile and that is when OP going to experience a major slow down. In addition, OP's new computer has a 9 years old processor Phenom 2 x4 840 compare to OP's old computer with i5 8250u that will destroy the 9 years AMD processor.