if it's a "was ok" scenario
money won't fix it - only improve short term
at work we don't just throw more and more ram at a machine - it could even make things worse
don't start throwing money away .... think what's changed ... because it was ok .... unless you have changed what you are doing - it should still be ok
when you are using the machine ... is the hard disc constantly "thrashing?
the most probable causes are HDD getting creaky and throwing errors
run chkdisk /f
in a dos window
THEN defrag
hdd getting over full - as above ... but add
http://www.ccleaner.com/download
run with default settings
you need to have at least 20% free diskspace (more=better)
if you have 10000000sof mp3 or jpg files ... shift them to cd/dvd... or wherever - just off the machine
a bloated file table (fat or mft) will really slow things down over a certain limit
if all this fails
crash and burn ...
easy to say ... if you aren't comfortable rebuilding the machine ... it's all a bit daunting
I tend to rebuild about every 12-18 months
but that's cause I can
if you have recovery discs that came with the machine ... it's not a huge job (once you've backed all your stuff up)