invisible mouse pointer

When using windows slide show and media center in full screen the pointer is
invisible, it senses the movement as the on screen navigation appears but no
mouse pointer. Other apps work fine DVD player etc in full screen mode it
seems that only these 2 apps are at fault. Have SP1 and all latest drivers
for Acer 7520 Laptop including Alps pointing device and Nvidia Graphics. The
mouse is a bit jumpy at times and does skip to a position sometimes after a
moment of freezing.
Also ,a little off topic but when connecting laptop aux/headphone out to an
external amplifier when on a/c power there is a pick up of sound from the
mouse hard drive and general squelch noise. There is no interference when
using battery power!
Any help appreciated TIA
KW