To remove text at the beginning of a sentence rather than somewhere inside the sentence, use the operator -replace and the anchor '^'. Check out the difference:
PS> 'PC101 is the PC we are overhauling' -replace 'PC','' 101 is the we are overhauling PS> 'PC101 is the PC we are overhauling' -replace '^PC','' 101 is the PC we are overhauling
