Windows OS , Bizarre File Pointer Fact

[Taygun Kekec]

Code :
#!/usr/bin/python
# -*- coding: utf-8 -*-
import os

if os.name == 'nt':
    OS_Selection = 0
elif os.name == 'posix':
    OS_Selection = 1
else :
    OS_Selection = 1

del_cmd_os = ( "del","rm")
filelist = ("ddd.txt","eee.txt","fff.txt")

# Creating Files
for elem in filelist:
    open( elem, 'w').write("Selam")

#
# Removing Files
for elem in filelist:
    fp = open( elem, 'r')
    os.system( "%s %s" % (del_cmd_os[OS_Selection], fp.name))
    fp.close()
#

Run this code on Windows XP , it says "the file is being used by
another process" and fails to delete the file. I tried replacing :
#
for elem in filelist:
    open( elem, 'w').write("Selam")
#
with :
#
for elem in filelist:
    fp = open( elem, 'w')
    fp.write("Selam")
    fp.close()
#

in case of any interpreter file pointer destructor failure but it
didnt change anything.
Do you have any idea why my files cannot be deleted from my disk with
2nd part of my code ?