Sony laptop problem. Performing properly?

Reinstall the OS and see if it helps.
4250 is weak but should handle those games perfectly fine

I've done multiple reinstalls in the past, those have never caused any improvement.

My friend's laptop specs say "Mobility 4200 series," but that completely outperforms this one. I always figured mine was just weak, but frankly it feels defective, given how inconsistent or pitiful performance is.

There are a few things you could check:

1) Fragmentation / Low free space on your HDD

You should always have a few GB free on you promary hard disk. If it gets too full and doesn't have enough space to work with the pagefile, you could see slowdowns. Also if it's almost full and very fragmented, it could cause you performance to degrade.

2) Overheating

Laptops are prone to overheating over time. The cpu cooler can gather dust between the fan and the cooler itself, resulting in almost zero airflow. That happened to me with an old hp with a 1,5 celeron and a measly 915 GML as a gpu. The normal temp was about 60 for the cpu but overtime it went up to 90 - 100! needless to say everything slowed down and started occasionaly freezing. After I opened the case and removed the dust, everything returned to normal.

3) Graphics settings

Check your driver settings. Maybe you accidentaly enabled something like AA that severely impacts performance (especially in 2d effects like smoke, explosions etc).

Excluding any actual hardware problems and according to what you said about removing bloatware and reinstalling the OS, it could very well be 2). Though it wouldnt hurt to run some hardware tests like memtest to see if everything is ok.

I have nearly 300 GB left.

Video settings are all set to use application settings. There's no VSync or AA on. All sliders are set to "use application settings or "Performance." I've had the hard drive replaced once, so it's not a hard drive error. It still detects the proper 4GB of RAM as well.

All I have left to try is checking for dust, but seeing as performance was always pitiful and never "normal," I don't really have high hopes. There are no signs of overheating and there never were. The best part, really the only good part I can say right now is that it's been pretty stable. Never turned off of its own accord, deleted my files, really done anything wrong. It's just painful when it comes to video performance. Performance has basically always been this bad, so if it were an overheating issue, I should have been seeking a refund 18 months ago. Perhaps most troubling is its refusal to even play videos at optimal framerate in fullscreen. Windows Media Player takes a couple seconds to load when I skip ahead, any videos online (youtube, blip, whatever) runs at sub-par framerate when at full screen.

Basically, the game I test the most is TF2. DX9 is nearly unplayable at anything but absolutely minimum settings, and even that drops into yellow on maps or in certain situations. I have to use DX8 and tweaks that make the game look like it's on PS1 to run consistently 30-60 fps. This computer should be capable of more.

Meanwhile, it continues to struggle with smoke effects in particular in older games (Max Payne, Freedom Fighters), and just hates 2d games. Super Meat Boy, while not quite a hugely scaleable game, should not be very demanding. It doesn't even list a minimum video card. But as usual, low resolution, reduced settings to make it run. Capsized does not even list a specified video card and is entirely 2d, yet causes unplayable mouse lag. Similar problem with Machinarium, a game made to run for the absolute lowest spec. Mouse lag. Noticeable and inexplicable mouse lag.
I don't even have anything to adequately describe the bizarre and inconsistent performance of this hardware.