problem with dllhost.exe

i have a problem, my computer is very slow and i notice that dllhost.exe is taking a lot of memory, i think my computer is infected, please help me, the thing is when i first open my computer it function normaly but when i try to open a folder and when i began to search and open and close other folders dllhost.exe shows up in the task manager and takes a lot of memory and the files appears without their icons.
i am sorry about my english, it's not my first or my second language.