What anti-virus program did you download and then uninstall? Do you know what sort of virus it had originally? It sounds like the malware is either still present or the uninstall of the anti-virus program deleted some vital OS files. Try booting into safe mode with networking and downloading "Malware Bytes," a free program. From there, run a scan and delete everything that it finds. Finally, restart the computer. If it continues to restart continuously, try running a windows start up repair via the windows CD or by accessing the recovery partition.