Sound Whistling

Recently my XP Home Edition computer has been updated to the following as detailed under my question.
My problem is that I receive a crackling and whistling through my speakers and microphone whenerver I play midi music, stored music on hard drive and playing a c.d.
When I remove the microphone from it's socket, everything plays perfectly. When I 'jiggle' the microphone in it's socket it crackles ?
Where is the problem happening ?

2.80 gigahertz Intel Pentium 4
16 kilobyte primary memory cache
256 kilobyte secondary memory cache
Board: ASUSTeK Computer INC. P5S800-VM Rev 1.xx
Bus Clock: 133 megahertz
BIOS: American Megatrends Inc. 1016.007 11/24/2005
480 Megabytes Installed Memory
Previously installed:
AOPEN CD-RW CRW5232 [CD-ROM drive]
HL-DT-ST CD-RW GCE-8240B [CD-ROM drive]
Maxtor 2F040J0 [Hard drive] (41.11 GB) -- drive 0, s/n F12A2N8E, rev VAM51JJ0, SMART Status: Healthy
SAMSUNG SV1022D [Hard drive] (10.20 GB) -- drive 1, s/n 0219J1DN828466, rev MK200-53, SMART Status: Healthy
SiS 7001 PCI to USB Open Host Controller (3x)
SiS PCI to USB Enhanced Host Controller
SoftV92 Data Fax Modem
Windows Media Player 9 SP0 FPRIVATE "TYPE=PICT;ALT=passed verification
Realtek RTL8139 Family PCI Fast Ethernet NIC