The following code does this better. You can select a value and display column. Also a method to free the memory allocated for the value objects.
Code by Steve Faleiro steve_goa@yahoo.com.

procedure disposeComboBoxObjects(c: TComboBox);
var
i: integer;
begin
if c.Items.Count > 0 then
for i := 0 to c.Items.Count - 1 do
Dispose(PVariant(c.Items.Objects[i]));
end;

// —- Populate a Combobox ———————————————
// —- for accessing the value, use:
// var
// s : PVariant;
// begin
// s := PVariant( lstServers.Items.Objects[lstServers.ItemIndex] );
// my_key := integer( s ^ ); // cast to your type
// ———————————————————————
procedure populateComboBox(c: TComboBox; ds: TDataSet;
KeyColumnIndex, DisplayColumnIndex: integer);
var
v: variant;
pt: PVariant;
begin

disposeComboBoxObjects(c);
c.Items.Clear;

with ds do begin
First;
while not EOF do begin
v := Fields[KeyColumnIndex].Value;
New(pt);
pt ^ := v;
c.Items.AddObject(Fields[DisplayColumnIndex].AsString, TObject(pt));
Next;
end;
end;

if c.Items.Count > 0 then
c.ItemIndex := 0;
end;

procedure disposeComboBoxObjects(c: TComboBox);
var
i: integer;
begin
if c.Items.Count > 0 then
for i := 0 to c.Items.Count - 1 do
Dispose(PVariant(c.Items.Objects[i]));
end;

// —- Populate a Combobox ———————————————
// —- for accessing the value, use:
// var
// s : PVariant;
// begin
// s := PVariant( lstServers.Items.Objects[lstServers.ItemIndex] );
// my_key := integer( s ^ ); // 0 then
c.ItemIndex := 0;
end;

procedure disposeComboBoxObjects(c: TComboBox);
var
i: integer;
begin
if c.Items.Count > 0 then
for i := 0 to c.Items.Count - 1 do
Dispose(PVariant(c.Items.Objects[i]));
end;

// —- Populate a Combobox ———————————————
// —- for accessing the value, use:
// var
// s : PVariant;
// begin
// s := PVariant( lstServers.Items.Objects[lstServers.ItemIndex] );
// my_key := integer( s ^ ); // 0 then
c.ItemIndex := 0;
end;