|mmm... All useful advice... and a bit more...?|
The first item to consider is data (files/stuff you wouldn't wish to lose...) and to preserve/safeguard it. Boot system (as per Jethro) with a linux variant on a CD/DVD. I tend to use knoppix or ubuntu; never heard of "Mint"... - new one for me...
Knoppix.com, Ubuntu.com - both a free ISO to download, which save to a hard-drive; then burn to a DVD; boot with that DVD.
This wil load itself into RAM only and leave system as is as a resource to that Linux OS. Access hard-drive and copy data off to optical-media and/or a an external hard-drive. Verify they are OK (accsessible) on at least one other system too.
Once data "safe" (and still booted via "Linux" variant) go to Trend.com and run "housecall" freebie scan; and let it run a full scan... It may take a while - so coffee/tea 'n toast/cream buns etc. time...? Anything it quaranitines - delete it.
Then reboot system as per norm and disable System Restore (as per Jeffiner); then - before loading/installing anything new in terms of clean-out utils etc... - go on-line again to Trend.com; again rerun their freebie Housecall util. As before... let it run a full scan (can take a while... - so time agtain for tea/coffee 'n toast etc..).
As before - anything it quarantines - delete it; then reboot - without System Restore enabled, and see what happens re' pests varoius. If things are better... then re-enable System Restore.
Why the double-scan at Trend? Mainly to ensure that when system is rebooted from XP and System Restore is still active (initially) it doesn't redeposit any nasties that it knew about... Disabling System Restore and then a rescan etc... will ensure that System Restore won't redposit anything nasty it "knew" about...
If no improvement then look at other scan utils. If you don't have Windows Defender installed then install and run it. It's the one decent util from M$-land that actually does wot is sez it duz...
A last resort is of course a restore to factory gate/delivery state; but don't go there untill all other avenues have been explored first. If you don't have the disks from Dell they will usuall replace them possible free - otherwise a wee sum);. And usually there is a reovery partition at the start of the drive too (a small "hidden" partition). This is usually accessed/run etc. via an F-key combination. A trip to Dell-land - or a browse of the user manual will elicit whath combinaation of keys to use to access/invoke the recovery routines various.
But first... safeguard data?