Is it worth upgrading my PC?

Hello all,

Apologies if this is a slightly facetious question, I am suffering from a little bit of knowledge regarding the subject.

I've had my desktop pc for the past 6 years and while it still runs adequately, it has become noticeably slower in certain departments (opening programs etc). However, I'm not sure whether to upgrade with new parts (I assume the cheaper option) or simply get a new computer altogether. I have already put new parts in before, installing a new graphics card and power supply. I'm not sure whether further new parts will just be prolonging the inevitable for a couple of years.

I guess what I am looking for is a simple yes/no answer as to whether it is worth shelling out for a new machine. I don't use it for hugely intensive games or programs (things like photoshop and Civ5 would be about the limit) but I would like it run faster it currently does.

Thanks in advance,

ant

Stats below:

Tech Support Guy System Info Utility version 1.0.0.2
OS Version: Microsoft® Windows Vista™ Home Premium, Service Pack 1, 32 bit
Processor: Intel(R) Core(TM)2 Duo CPU E4700 @ 2.60GHz, x64 Family 6 Model 15 Stepping 11
Processor Count: 2
RAM: 2045 Mb
Graphics Card: NVIDIA GeForce GTS 450, -2048 Mb
Hard Drives: C: Total - 294940 MB, Free - 133869 MB; D: Total - 10239 MB, Free - 6041 MB; F: Total - 953868 MB, Free - 817476 MB;
Motherboard: Dell Inc., 0RY007
Antivirus: avast! Antivirus, Updated and Enabled