The important thing to understand about UBM is that it's a metric of performance from the systems that have run the benchmark, and it's ever changing.
If you had a system that was 110% on everything, you wait a couple of years and it's 90% on everything, because the performance of equipment running the benchmark have gotten better. Your system is fairly old and not super high spec to begin with.
Something that helps when running benchmarks is to turn off everything else running in the background. You are showing 16%, which isn't helping to score higher.
This computer is on a level where it should be good for surfing, media consumption, productivity, and VERY light gaming on stuff that is older and/or easy to run.
In what way do you feel that your pc is performing poorly?
If it is for fast action games, your GT730 is the limiter.
GT730 comes in 2 and 4gb versions which can make a difference in capability.
Also the GDDR5 version will be faster than the GDDR3 version.
Regardless, GT730 is considered as only minimally competent as a gamer.
You are using Hard drives.
Substituting a ssd for your windows C drive will make a major difference in overall quickness.
What is your cpu temperature at idle?
If it is higher than 10-15c, over ambient, your cooler might have come loose causing thermal throttling and low cpu performance.
If you were looking for better gaming performance, the first thing to upgrade is the video card. The GT 730 DDR3 is not really a card you can run the latest games even on the low preset at 720p and expect decent results.
The second part to upgrade may be the CPU, but at the point where you're at if you can't find an i7-4790K (and possibly a cooler upgrade), I'd suggest simply upgrading everything. Although the i7-4790K path should only be considered if you have a decent H87 or Z87 board. Otherwise adding another 8GB of RAM may help depending on how many background apps you want to have open while you game.
Upgrading storage would be useful for helping your computer feel snappier and reducing loading times, but it generally doesn't affect in-game performance.
I5 3340 base clock is 3.1GHz. Turbo is 3.3GHz. You are running with turbo disabled, so will get worse performance than anybody else with the same cpu.
You have a 160Gb hdd that's closer to 10 years old when new. It's probably worn out, grease is getting thick/gone, belts stretched, it's slowing down as it's way past its physical life expectancy.
Not sure what is going on with the ram, but my guess is that it's run single channel and/or timings are on the far end of the scale.
You've got Grandpa with a cane. Doesn't matter what you do, he'll never run the hundred yard dash. The only thing you can do is use the info provided by UBM and go through each component individually and see Why each is slow in comparison. Some things you can fix, others you cannot.