Sudden duplicates of rundll32.exe since 12th Dec

I have eleven instances of RUNDLL.EXE – IA853552 etc, in C:\WINDOWS\Prefetch, all of which have been added since 12th December.

They are 15-32kb in size, one is 30.9-32kb

I have searched for information and realise that in essence it is an essential program file name, but this coincides with intermittent internet access where there doesn’t seem to a be problem with the network, router or line.

Should I be treating this as a trojan? There is mixed information but the timing seems odd.

Many Thanks,
Emma