for one, use FOXIT reader, instead of Adobe Acrobat, uses WAY LESS resources.
As for slow start-up, it's probably because Dell bloated your computer with tons of trial software you don't need ie - AOL, GOOGLE DESKTOP, Netware, etc, etc...
Task bar manager, dont know what's going on with that.
Also, IF you're good with BIOS setups, you may want to change the order in which your computer boots up.
Your CD/DVD-ROOM or floppy drive may be first in the boot up order, usually I put my hard-drive first to boot, which makes it faster.
But ONLY do this IF you're comfortable entering the BIOS and know what you're doing.

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@ROTAXPOWER wrote:

Well my 8500 is extremly slow, it takes for ever to boot up, and I have problems useing acrobate reader. Also when I push Ctrl, ALT, DEL, My task manager does not pop up, only the process tree does, what could the problem be? Thanks for helpin'!

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Try to run System File Checker (SFC). It will check the system files and replace it with original version. Just get ready the XP CD.

To run the SFC: Boot to Windows. Start>Run then type cmd.exe in run box. Hit OK.
In command prompt, type SFC /scannow
It will ask for XP CD. Insert it in your optical drive.

See if that will make the Task Manager to work again. If that doesn't help, make sure that your task manager isn't running in tiny footprint mode.

Also, spyware and other type of malware can caused slow system and/or corrupt system files. Run a full system scan using Spybot Search & Destroy or Windows Defender. Also scan using your antivirus software. Make sure to update your Windows when the scanners found no infection.