My laptop's 5400 RPM disk drive feels... lethargic during boots and app loads, and I see some freezing during first loads of applications after boot.

Should I replace the disk drive? If so, what should I get? A 7200 RPM disk drive, a hybrid disk drive, or a pure SSD, knowing that the 750 GB drive is currently filled with over 210 GB of data, and I'm actually looking to improve boot times and app load times only. Factor cost and the fact that there is only one standard SATA drive bay (9.5 mm high), no PCI-e slots, and a non-user-removable optical drive (I need it anyway).

Umm, no. You're not going to get any benefit from that. Try living with an 80 gig internal drive.

No. It does, however, sound like you could use a fresh OS install or more ram. At least, that's what I did; took the ram in one laptop and used it as an extension to the other one. Haven't regretted it since.

Since I already have 8 GB of RAM, I decided to do some benchmarking on my laptop's boot times, but first things first - I did a System Restore point creation just in case I turn off some essential service or the OEM apps that I must never disable...

I've also cleared the temporary files folders and also any Prefetch/ReadyBoost/ReadyBoot data.

Then I let it reboot once. Predictably, the first boot is very slow due to no cached data being present. After the first boot is fully complete, I repeated the process around 5 times. With each successive reboot, the boots and shutdowns become progressively faster - the time to desktop cuts down nicely.

After doing it five times, I give the computer a nice shutdown, waited for ten seconds after the power LED went off, and then I turned it on, with my feature phone's stopwatch app also being ran at the same time.

I did it several times to give me a sense of proper timing, and including the POST time:

Power on until POST finishes: 8.1 seconds
Power on until "Starting Windows" disappears: 30.2 seconds
Power on until desktop is loaded: 68 seconds
Power on until the entire thing is loaded with no more disk I/O: 244 seconds

Seems like I need to cut down the time between "desktop loaded" and "complete boot". Perhaps I should give Autoruns a look. I've also noticed that if I give the computer time to boot completely (4 minutes), no app thrashes.

(By the way, how does that compare to your computer?)

Anyway, perhaps I should put off getting an SSD for now, as I explore other options.

Reinstall Windows and avoid having a lot of stuff that starts at boot. My ancient laptop is faster than that.

Let's see... Hmm, Autoruns is quite powerful, in that it can actually remove hooks from Winlogon.

I've disabled a lot of processes and, well, after five tries (of course, caches are busted first, and I've also made my laptop to use fast boot):

Power on until POST finishes: 6.7 seconds
Power on until "Starting Windows" disappears: 27.5 seconds
Power on until desktop appears: 55.4 seconds
Power on until boot completes: 92.4 seconds

Is this much better?

Mine often takes a really long time to boot, at least 5 minutes. I've disabled quite a few startup processes, and defragged the C drive, but I haven't been able to benchmark boot time after that.

Maybe I should sometime soon.