A 7 year old machine is getting quite long in the tooth.
Maybe, maybe not. Per-core performance has basically flat-lined for the last 7 years. Long-gone are the days where clock speeds doubled every 12-18 months or where buying a new PC would get you something that ran 4-8x faster then the one you had from 3-4 years ago.
At the moment, I'm still using a 2007-era Thinkpad T61p (Core2 Duo 2.2GHz, 8GB RAM, Win7 Pro, SSD). It originally shipped with WinXP, 4GB RAM and a 7200 RPM HD. This is still the machine I use for the majority of my work.
The main advantage I have is that before the 4yr warranty ran out, I made *sure* to have it serviced, so it has a new backlight, new keyboard (which was acting up), etc.
Is it slow? Eh, the CPU is not the zippiest and I would definitely prefer a faster quad-core, but it still works well enough that I'm not ready to spend $2200 on a new Thinkpad. I have a much more powerful desktop sitting beside me for things that need raw CPU power.
Really, the thing that makes it still usable is the SSD. Without that I would have given up on it years ago. It's why we are putting SSDs on all the desktops at the office. With a good SSD, you spend a lot less time twiddling your fingers and less fear that if you do X that you can't do Y at the same time because of disk contention.