Why is my PC running slow?

Move the Page File to the second HDD and use a good Defragmenting Program to Defragment the HDDs

You will need to run the Defrag Utility several times.

Now for the obvious things according tot he service Manual this unit will only take 2 gig of RAM in the form of 2 x 1 GIG Modules. These 2 Modules should be identical and you should have RAM installed in Pairs to get Dual Chanel Mode which is the fastest that the system can run at.

As for whats happening here it depends on what CPU you actually have as there where several available for this ranging from a 2.8 GHZ to a Celeron 340 Processor.

If you have a Celeron CPU it would be better to get one of the full Pentiums and fit that as Celerons are considerably slower than a Full Intel CPU.

You may also need to look at the type of HDD that you have and how they are configured here. If you have a slow speed IDE Drive and then have 2 IDE Drives on the same Chanel the fastest will default to the same speed as the slowest HDD you have on that IDE Data Lead and this will also slow things down.

And just for reference here is the Service Manual

http://support.dell.com/support/edocs/systems/dim3000/en/sm/specs.htm

Col

I'm running on some old machine too and it fills my needs so I suggest you to do something else.
Defrag is sap, also empty some space on c: 80% full tops.
Move virtual memory to d: and set it to 2GB
Update your windows.
Run CClean, clean unnessery files an registery
See in task manager what causing 100% cpu and google it.
Run some antimalware program. Antimalware I'll suggest:
- Spybot Search and destroy
- Malwarebytes' Anti-Malware
- SUPERAntiSpyware
- Microsoft Security Essentials
- ComboFix **but read instructions first because it can kill your system if you're not careful**
All of these are free or shareware so you can install it and run for free.
This is a all day job on old computers but it worth's it
I have Sempron 2600+; 1.5GB RAM (2x256 + 2x512 in dual mod); Radeon 9550; 3 IDE HDDs (2 SATA 1 PATA); Windows XP pro 3 years old and it runs like snap. Only thing I that causes "problems" is heavy flash websites but I learned to dill with it with some Firefox tweaking and extensions.

I would run disk clean up. It may take a long time. I use Ultradefrag and it is very good.
See if the computer runs better. If so, run the two apps every weeks.
A desktop computer froze in opening an application. I ran disk clean up and it opened right away.

Swap on D:\ instead of C:\, run Auslogics Disk Defrag and Auslogics Registry Cleaner (both FREE and quite potent), try to upgrade to Win7 (on a Celeron...ehh, might work..?), download Autoruns from Microsoft (also FREE) and essential for cleaning up Startup routines, lastly do ALL updates. Alternatively, take prior suggestions about installing a Pentium and doing a proper pairing of RAM modules.

A lot of good ideas above, except I don't think updating to Win 7 would help - it uses more resources than XP, probably be even slower. MyDefrag is the best defrag utility I've found, though Auslogics is also good.

After you've installed the right RAM, done the cleanups, run the malware scans, I'd suggest running CheckDisk if you haven't recently. Usually helps my old computer, fixing accumulated file system errors.

Run SmartDefrag ver 2.1, Its free and it does "wonders"...

I think some malware programs are running......Which operating system you are using?

Or did I misunderstand you?