Not really a hardware issue but I don't know where else to post it.

Today i got an email in my yahoo account from the address 'support@yahoo.com' with the subject 'Account Suspension.' It looked legit so i opened it. The body of the e-mail said something along the lines of 'Your account has recently been used to send a vast amount of spam emails. Please download the attached file and review its contents or your account will be suspened.'
I followed the instructions and the file installed a searchbar called 180Search Assisstant on my computer. I think I got rid of that but now there's this thing called Slotchbar which opens up a pop up window every time i boot up. I found a fix tutorial online that tells me to remove certain entries in the Add/Remove Programs list. I attempted to remove them but I am unable to. One of them, which is called ISTsvc will open up a window when I click remove but the window will remain only for a second and then disappear. The other entry I was told to remove is called SlotchBar. When I click remove, nothing happens. The fix tutorial also told me to install and run a program called HijackThis. I installed it but when I run it, it opens for a second and then disappears. I have run Spybot S&D and SpySubtract but neither has fixed this problem. Any help is appreciated.