What exactly are you using your computer for?? If its for
mundane office stuff like spreadsheets, word processing, sending
emails etc, i don,t see any reason why you are not able to cope
with that PC of yours.
Of course if you are talking about video conferencing, multimedia,
programming etc then you need a new PC. Alternatively , try
googling on "how to make your computer faster". There are some
nifty tricks that can "rejuvenate" an old & ailing PC.