Can detect viruses only Format "C" partition

i believe my PC already inflected by viruses or mall-ware , so i want to know can i disinfectant or detect or delete them Only format my PC "C" partition i mean again installed O.s. and then again installed antivirus software then can i detect virus etc in other partitions in my hard disk. because other partitions contain lots of files so i don't like to format all partitions.

if it could be useful?