Post the code.  Also, have you tried turning off screenupdating and calculation
whilst it is running, and then putting it back on at the end:-

Sub xyz()

Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual

   Code................

Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic

End Sub

Various examples of code to delete rows:-

Sub DlBlnks()

On Error Resume Next     ' In case there are no blanks
Columns("A:A").SpecialCells(xlCellTypeBlanks).EntireRow.Delete
ActiveSheet.UsedRange 'Resets UsedRange for Excel 97

'more information in
'Delete Cells/Rows in Range, based on empty cells, or cells with specific values
'http://www.mvps.org/dmcritchie/excel/delempty.htm
End Sub

-----------------------------------------------------

Public Sub DeleteReallyBlankRows()
'Chip Pearson
'Will delete all rows that are entirely blank
Dim r As Long
Dim c As Range
Dim n As Long
Dim Rng As Range

On Error GoTo EndMacro
Application.ScreenUpdating = False
Application.Calculation = xlCalculationManual

If Selection.Rows.Count > 1 Then
   Set Rng = Selection
Else
   Set Rng = ActiveSheet.UsedRange.Rows
End If
n = 0
For r = Rng.Rows.Count To 1 Step -1
   If Application.WorksheetFunction.CountA(Rng.Rows(r).EntireRow) = 0 Then
       Rng.Rows(r).EntireRow.Delete
       n = n + 1
   End If
Next r
EndMacro:
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub

-----------------------------------------------------

Sub DeleteEmptyRows()
'John Walkenbach
'Will delete all rows that are entirely blank
   LastRow = ActiveSheet.UsedRange.Row - 1 + _
       ActiveSheet.UsedRange.Rows.Count
   Application.ScreenUpdating = False
   For r = LastRow To 1 Step -1
       If Application.CountA(Rows(r)) = 0 Then Rows(r).Delete
   Next r
End Sub

-----------------------------------------------------

Sub DeleteEmptyRows2()
'John Walkenbach Edited
'Will delete all rows where E:AI is entirely blank
   LastRow = ActiveSheet.UsedRange.Row - 1 + _
       ActiveSheet.UsedRange.Rows.Count
   Application.ScreenUpdating = False
   For r = LastRow To 1 Step -1
       If Application.CountA(Cells(r, 5).Resize(1, 31)) = 0 Then Rows(r).Delete
   Next r
End Sub

-----------------------------------------------------

Public Sub DeleteBlankRows():
'This will delete all the blank rows if cell in Col A is blank within the active
sheet.

       On Error Resume Next
       Intersect(ActiveSheet.UsedRange.EntireRow, Columns(1)).SpecialCells( _
               xlCellTypeBlanks).EntireRow.Delete
       On Error GoTo 0
End Sub
Public Sub DeleteSelectionBlanks():
'This will delete all the blank rows contained within a selection of blank rows.
'Select by dragging down on the row handles to select entire range containing
rows
'you wish to delete.

       On Error Resume Next
       Intersect(Selection.EntireRow, Columns(1)).SpecialCells( _
               xlCellTypeBlanks).EntireRow.Delete
       On Error GoTo 0
End Sub

-----------------------------------------------------

Sub DelRows1()

ans = InputBox("What string do you want rows to be deleted if they contain it?")
Application.ScreenUpdating = False

LastRow = ActiveSheet.UsedRange.Row - 1 + _
       ActiveSheet.UsedRange.Rows.Count

Set Rng = Range(Cells(1, "A"), Cells(LastRow, "A"))

With Rng
  .AutoFilter
  .AutoFilter Field:=1, Criteria1:=ans
  .SpecialCells(xlCellTypeVisible).EntireRow.Delete
End With
Application.ScreenUpdating = True

End Sub

-----------------------------------------------------

Sub Delete_Rows()

Dim RowNdx As Long
Dim LastRow As Long

LastRow = ActiveSheet.Cells(Rows.Count, "A").End(xlUp).Row
For RowNdx = LastRow To 1 Step -1
       If InStr(UCase(Cells(RowNdx, "A").Value), "OLD") Then
           Rows(RowNdx).Delete
       End If
Next RowNdx

-----------------------------------------------------

End Sub
Sub DelBlankLookingCells1()
'Note:- Cells not rows
Dim Rng As Range
Dim cel As Range
Dim DelRng As Range
Set DelRng = Nothing
Set Rng = ActiveSheet.UsedRange

For Each cel In Rng
 If Len(Trim(cel.Value)) = 0 Then
     If DelRng Is Nothing Then
        Set DelRng = cel
     Else
        Set DelRng = Union(DelRng, cel)
     End If
 End If
Next
If Not DelRng Is Nothing Then
  DelRng.Delete Shift:=xlToLeft
End If
End Sub