I had a similar issue. I had a miner doing 190 MH/s and I was mining ETC. When the DAG reached 3.8 GBs (EPOC 364, Support ends @ 384)
In my system, #373 dag is the last 4gb can mine on windows. We are at moment on dag #353, that is 20 dags which is 4 x 20 = 80 days + 4 days = 84 days, by my calculations, 4gb gpus will mine till 26 october 2020 #dag 374 on windows and 27 november 2020 on systems that let you use 4gb fully.