Continuing installation after errors (SAP Netweaver: ABAP_7_03_SP04_64_bit_Trial_3_9_2_GB)

Hi. I continue to have multiple errors while trying to install the package above, using "sapinst". Suppose I can solve an error, how do I continue the installation at the point were it was halted? I now restart "sapinst", but that takes the procedure from step one, which invariably runs into the problem that the system says that there's already SAP systems installed.

The first time I tried the installation, almost all of the 23 installation tasks were executed without any problem, till it threw an error at the last task (the one on "reports"). At consecutive attempts new errors have occurred, much earlier in the process, no doubt because of files/systems that had already been installed.

So my other question is, how can I delete from my system anything that was already installed through these botched installations, so I can start over with a clean slate? After depleting the usual "uninstall" functions, I even tried reinstalling Windows 10, but still, that didn't help. Amazingly, there are still SAP files lurking in the system, which continue thwarting further installation attempts.

My system is a Windows 10 laptop, 64bit, 4 GB RAM, and 500 GB free hard disk space. I'm trying to install the SAP AS for autodidactical purposes.