well if ur having problems with other drivers then perhaps u r having a conflict...
bottom line, u either have to use a mod driver like the ones available here or use the hp vers.
bty, newer doesnt always give u 'better perf'. as soon as they come out with a newer gpu ati/nv tend to 'forget' about their older cards. i have seen newer releases actually impede perf on older cards.
have u asked your question in here -
Driver Heaven Mobility Modder.net Public Beta V 0.8.8.0 - XP and Vista Support! ?
anyway, gl.